GLP-1 Glossary
149 terms, put into plain English: the drugs, the trials, the mechanisms, the side effects, the pharmacy vocabulary and the dosing. Each entry links through to the GLP Watchdog article holding the primary-source evidence.
The glossary sits inside the wider GLP Watchdog register: 270+ research articles, plus 570+ GLP-1 telehealth providers under clinical review. Two kinds of source go into all of it, FDA labels and peer-reviewed literature indexed on PubMed, and nothing else does.
Drugs and brands
Every GLP-1 the FDA has approved, and the active ingredient inside each one.
- Wegovy
Semaglutide sold as a weekly injection for weight management, approved by the FDA in 2021 and dosed 0.25 to 2.4 mg. Same molecule as Ozempic, aimed higher. Worth knowing when you shop: a compounded seller advertising “semaglutide” is not selling you Wegovy, and the price gap between the two is the largest in this market.
- Ozempic
Semaglutide sold as a weekly injection for type 2 diabetes at 0.5, 1 and 2 mg. Chemically identical to Wegovy, approved for a different job, and prescribed off-label for weight loss constantly. The brand name turns up in advertising far more often than in the vial.
- Rybelsus
Semaglutide as a daily tablet at 3, 7 and 14 mg, approved for type 2 diabetes. It is also the drug behind the 33% levothyroxine AUC interaction warning. The oral route is the whole complication: it only absorbs under strict fasting conditions, which is why sellers offering “oral semaglutide” owe you a straight answer about what is actually in it.
- Saxenda
Liraglutide 3.0 mg, injected daily rather than weekly, approved for weight management in 2014. Its half-life is about 13 hours, which is the entire reason for daily dosing. Largely superseded commercially, and priced accordingly.
- Zepbound
Tirzepatide sold as a weekly injection for weight management, approved 2023. A dual GLP-1/GIP agonist, and the trial number people quote: about 21% body weight reduction at 15 mg in SURMOUNT-1. The most expensive brand in this register and the one compounded sellers most often position against.
- Mounjaro
Tirzepatide sold as a weekly injection for type 2 diabetes, approved 2022. Identical molecule to Zepbound with a different label, and it carries the same four-week backup-contraception warning for anyone on oral hormonal contraceptives.
- Foundayo
Orforglipron tablets from Eli Lilly, FDA-approved April 2026 as the first oral non-peptide GLP-1 receptor agonist. Taken daily on an empty stomach with a 30-minute wait. Its arrival matters commercially: a pill with no cold chain and no needle changes what a telehealth seller has to justify charging for.
- Semaglutide
The active ingredient in Wegovy, Ozempic and Rybelsus. Its roughly seven-day half-life is what allows weekly injection. When a seller lists “semaglutide” at a fraction of brand pricing, they mean a compounded preparation of this molecule, not the approved product — a distinction their pricing page often blurs.
- Tirzepatide
The active ingredient in Mounjaro and Zepbound, a dual GLP-1 and GIP agonist with a roughly five-day half-life. It is the only injectable in the class carrying an FDA-mandated oral contraceptive interaction warning, which is a real thing to raise with a prescriber rather than a footnote.
- Orforglipron
The generic name for Foundayo, and the first non-peptide GLP-1 agonist to reach approval. Its contraceptive interaction works differently from tirzepatide's — co-localization in the GI tract rather than delayed gastric emptying — so the two warnings are not interchangeable.
- Retatrutide
Eli Lilly's investigational triple agonist (LY3437943), hitting GLP-1, GIP and glucagon receptors. Phase 2 (NEJM 2023, Jastreboff et al., PMID 37366315) reported up to 24.2% weight reduction at 48 weeks. ⚠ The widely quoted 28.7% figure is from TRIUMPH-4 and comes from a Lilly TOPLINE PRESS RELEASE of 11 December 2025 — obesity with knee osteoarthritis, 12 mg, at 68 weeks — not from a peer-reviewed publication; the TRIUMPH papers indexed so far describe the trial DESIGN (PMID 41090431). The same release reported dysesthesia in 20.9% of the 12 mg arm against 0.7% on placebo. Not approved. ⛔ It is sold anyway, as “research peptide”, by sellers this register does not list.
Open the term page →Retatrutide: Lilly's triple agonist evidence →
- CagriSema
Novo Nordisk's investigational fixed-dose pairing of cagrilintide with semaglutide. In REDEFINE 1 it produced average weight loss of 20.4% by week 68, or 22.7% under the adherent estimand, where semaglutide by itself managed 14.9%. An NDA is filed. Novo had guided to 25%, so the figure disappointed against its own forecast while still beating semaglutide, which is why write-ups of it swing either way depending on the author.
- Cagrilintide
Novo Nordisk's long-acting amylin analog, on a different receptor pathway from GLP-1 entirely, signaling satiety through the brainstem. Studied alone at 11.5% weight loss over 68 weeks in REDEFINE 1, and as the second half of CagriSema.
- Survodutide
Boehringer Ingelheim and Zealand Pharma are developing this one, an investigational agonist hitting both the GLP-1 and glucagon receptors. Phase 2 reported up to 19% weight loss at 46 weeks and the phase 3 SYNCHRONIZE program is enrolled. Not approved.
Open the term page →GLP-1 pipeline: survodutide, MariTide, ecnoglutide →
- MariTide (Maridebart Cafraglutide)
Amgen's investigational once-monthly conjugate, maridebart cafraglutide, pairing a GLP-1 agonist with a GIP ANTAGONIST. Phase 2 (NEJM 2025) reported 16–20% weight loss. The GIP direction is the opposite of tirzepatide's, which is why it is interesting rather than incremental. Not approved.
Open the term page →GLP-1 pipeline: survodutide, MariTide, ecnoglutide →
- Ecnoglutide
A biased GLP-1 receptor agonist from Sciwind Biosciences, licensed to Pfizer for China. Phase 3 SLIMMER reported positive results in Lancet Diabetes Endocrinology 2025 and it is approved by China's NMPA. Not FDA-approved and not in active US development — relevant mainly because the name turns up on gray-market listings.
Open the term page →GLP-1 pipeline: survodutide, MariTide, ecnoglutide →
- Liraglutide
The daily GLP-1 behind Saxenda and Victoza. Older, shorter-acting and largely priced out by the weekly drugs, though it still appears where supply or cost rules out the newer options.
- Exenatide
The first GLP-1 receptor agonist to market (Byetta, Bydureon), derived from a compound in Gila monster venom. Now essentially historical in weight management, but it is the reason the class exists at all.
- Dulaglutide
Trulicity, a weekly GLP-1 for type 2 diabetes. Not approved for weight management, and not what a compounding seller is preparing, though it turns up in insurance step-therapy rules as the cheaper thing you must fail first.
- Albiglutide
Tanzeum, a weekly GLP-1 withdrawn from the market in 2018 for commercial reasons rather than safety. Its outcomes trial, HARMONY OUTCOMES, still counts as class evidence.
- Contrave
Naltrexone plus bupropion, an oral non-GLP-1 weight-loss drug. Cheaper than a GLP-1 and much less effective; it shows up as the option an insurer wants you to try first.
- Qsymia
Phentermine plus topiramate, an oral weight-loss combination. Same commercial role as Contrave: the older, cheaper thing a formulary may put in front of the drug you asked for.
- Bupropion
An antidepressant that also blunts appetite, and half of Contrave. Relevant here mostly because it interacts widely, so it belongs on the list you hand a prescriber.
- Naltrexone
An opioid antagonist used at low dose in Contrave. Also sold on its own by some telehealth operators as a weight-loss adjunct on much thinner evidence than a GLP-1.
- Phentermine
A short-term appetite suppressant and a controlled substance, half of Qsymia. Some sellers in this market bundle it alongside a compounded GLP-1, which changes both the risk profile and what the monthly price is buying.
- Topiramate
An anticonvulsant that suppresses appetite as a side effect, the other half of Qsymia. Carries real teratogenic risk, which is why the pregnancy questions on an intake form are not a formality.
- Pemvidutide
Altimmune's investigational GLP-1 and glucagon dual agonist, in development for obesity and MASH. Not approved.
- Mazdutide
Innovent and Eli Lilly's investigational GLP-1 and glucagon dual agonist, developed principally for the Chinese market. Not FDA-approved.
Mechanism
What a GLP-1 receptor agonist actually does: which receptors it reaches, how it slows gastric emptying, and the satiety pathway it runs through.
- GLP-1 receptor
The G-protein coupled receptor that responds to glucagon-like peptide-1. Activating it suppresses appetite, slows gastric emptying and improves glucose-dependent insulin secretion. Every drug in this register works on it; what differs is what else they touch.
- GIP receptor
The glucose-dependent insulinotropic polypeptide receptor. Tirzepatide agonizes it alongside GLP-1, which is the proposed reason its gastric-emptying delay runs deeper than semaglutide's — and, downstream, why its side-effect profile is not simply a stronger version of the same thing.
- Dual agonist
A drug hitting two receptors at once. Tirzepatide (GLP-1/GIP) is the one on the market; CagriSema and survodutide (GLP-1/glucagon) are in late-stage trials. Useful vocabulary when a seller describes a compounded product as “dual action” without saying which two receptors they mean.
Open the term page →GLP-1 pipeline: survodutide, maridebart, ecnoglutide →
- Gastric emptying
How fast food and oral medication leave the stomach. GLP-1 drugs slow it down, and that single mechanism does triple duty: it is the appetite suppression people want, the nausea they do not, and the reason the oral-contraceptive and levothyroxine interactions exist.
- Food noise
The patient term for constant intrusive thinking about food. Most people on a GLP-1 report it quieting within the first four to eight weeks. Not a formal medical term, widely reported in cohort studies, and heavily used in advertising precisely because it describes the thing people actually want.
- Triple agonist
A peptide activating three metabolic receptors at once, typically GIP, GLP-1 and glucagon. Retatrutide is the first in clinical development for weight loss, with the glucagon arm hypothesized to add energy expenditure on top of appetite suppression. ⛔ None is approved, which does not stop them being sold.
- Amylin
A pancreatic hormone co-secreted with insulin that signals fullness through the brainstem, a different pathway from GLP-1 entirely. Long-acting analogs such as cagrilintide are being tested alone and stacked with semaglutide to push weight loss past what GLP-1 alone reaches.
- GLP-1 tachyphylaxis
Weight loss flattening at a stable dose as the drug's effect wears down: pharmacological tolerance. Documented in rodent models and clinically suspected in the roughly 20% of long-term users who stall short of their goal while still dosing. Proposed mechanism is receptor downregulation or β-arrestin desensitization. ⚠ Microdosing protocols and drug holidays get sold as the fix; no randomized data support that.
- Non-peptide GLP-1 agonist
A small organic molecule that switches on the GLP-1 receptor without being built from a peptide chain, so it survives stomach acid intact and needs none of the absorption scaffolding oral peptides require. Foundayo (orforglipron) was the first FDA-approved one, in April 2026.
- A1C (glycated hemoglobin)
Glycated hemoglobin: average blood glucose over the prior 8–12 weeks, read as the percentage of hemoglobin glycated by glucose. ≥6.5% is diabetes, 5.7–6.4% prediabetes, under 5.7% normal. GLP-1s typically drop it 1.0–2.0 points at full dose, and each point is worth roughly a 25–35% cut in microvascular complication risk.
- MASH / MASLD
Metabolic Dysfunction-Associated Steatohepatitis and Steatotic Liver Disease, the 2023 renamings of NASH and NAFLD. Liver fat with inflammation (MASH) or without (MASLD), driven by insulin resistance and obesity. SYNERGY-NASH (Loomba 2024 NEJM, tirzepatide) and ESSENCE (semaglutide phase 3) both showed substantial fibrosis improvement.
Open the term page →Tirzepatide trial reading list (incl. SYNERGY-NASH) →
- TBWL (Total Body Weight Loss)
Total body weight loss: the percentage of starting weight lost, and the primary endpoint modern obesity trials report. STEP-1: −14.9% on semaglutide 2.4 mg at 68 weeks. SURMOUNT-1: −20.9% on tirzepatide 15 mg at 72 weeks. Reported as a percentage rather than kilograms because 15% means the same metabolic thing whether you started at 100 kg or 200 kg.
- C-peptide
A fragment released by the pancreas one-for-one with your own insulin, used to tell who is still producing it. GLP-1s work by amplifying endogenous insulin secretion, so people with very low C-peptide (under 0.6 ng/mL) tend to respond poorly — part of why the class is labeled for type 2 rather than type 1 diabetes.
- eGFR (estimated glomerular filtration rate)
Estimated glomerular filtration rate, the standard read on kidney filtration, in mL/min/1.73m². Normal sits at 90 or above. Anything under 60 sustained across three months is what defines chronic kidney disease; stage 4 runs 15–29 and stage 5 falls below 15. In FLOW, semaglutide cut major kidney-disease events by 24% among diabetic patients whose kidneys were already failing (Perkovic 2024, PMID 38785209), and that is what drove the 2025 Ozempic label expansion.
- Visceral adipose tissue (VAT)
Fat packed deep in the abdomen around the liver, pancreas and intestines, as opposed to the subcutaneous fat under the skin. It is the metabolically dangerous kind. DEXA substudies of STEP-1 and SURMOUNT-1 found GLP-1s strip it preferentially, which helps explain why cardiometabolic risk falls faster on these drugs than on calorie restriction reaching the same weight.
- AHI (apnea-hypopnea index)
Apnea-hypopnea index: breathing pauses of ten seconds or more, plus partial reductions with oxygen desaturation, counted per hour of sleep. 5–14 is mild obstructive sleep apnea, 15–29 moderate, 30 or more severe. SURMOUNT-OSA used it as the primary endpoint and tirzepatide 15 mg cut it by about 25 events an hour against placebo.
- SNAC (oral semaglutide absorption enhancer)
Sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, the absorption enhancer formulated alongside oral semaglutide in Rybelsus. It nudges gastric pH and loosens the cell membrane just enough for a peptide to cross; without it oral semaglutide absorption is effectively nil. That is the real reason for the 30-minute fasting window — food breaks the complex. ⚠ Worth asking any seller offering “oral semaglutide” what they use in its place.
Major trials
The Phase 3 trials that won approval, and the outcome studies that came afterward on cardiovascular, kidney and sleep-apnea endpoints.
- STEP-1
Semaglutide 2.4 mg weekly against placebo, the pivotal phase 3, run across 1,961 participants carrying excess weight (Wilding et al., NEJM 2021, PMID 33567185). Average loss reached 14.9% by week 68. Nearly every piece of semaglutide marketing you encounter rests on that figure, compounded products included, though none of those were in the trial.
- SURMOUNT-1
Tirzepatide at 5, 10 and 15 mg weekly against placebo, the pivotal phase 3, run across 2,539 participants carrying excess weight (Jastreboff et al., NEJM 2022, PMID 35658024). The 15 mg arm averaged 20.9% loss across 72 weeks. That is the result that turned tirzepatide into a drug people request by name.
- SELECT
Ran semaglutide 2.4 mg against placebo in an enrolled population of 17,604 people who were overweight or obese and already had cardiovascular disease, none of them diabetic (Lincoff et al., NEJM 2023). Major adverse cardiovascular events fell 20% (HR 0.80, 95% CI 0.72–0.90). That result is the reason the drug now gets argued about as cardiac prevention instead of cosmetics.
- FLOW
Semaglutide 1 mg weekly in chronic kidney disease with type 2 diabetes (NEJM 2024). Its combined kidney endpoint, counting eGFR decline, kidney failure, and renal or CV death, fell 24% (HR 0.76).
- SURMOUNT-OSA
Tirzepatide 10/15 mg weekly in obstructive sleep apnea with obesity. The apnea-hypopnea index improved roughly 50% against placebo, which is the kind of result that changes what a sleep clinic prescribes.
- STEP-TEENS
Semaglutide 2.4 mg in adolescents aged 12–17 with obesity (Weghuber et al., NEJM 2022). Mean weight reduction 16.7% against 0.6% on placebo. ⚠ Pediatric trials do not measure facial appearance, so anyone citing this trial alongside “Ozempic face” claims is welding two unrelated things together.
- MACE (Major Adverse Cardiovascular Events)
Major adverse cardiovascular events, the composite endpoint CV trials are built on, usually cardiovascular death plus nonfatal myocardial infarction plus nonfatal stroke. SELECT showed a 20% relative reduction, SUSTAIN-6 26%, LEADER 13%. The effect tracks weight loss loosely but exceeds what weight loss alone accounts for.
- KCCQ-CSS (Kansas City Cardiomyopathy Questionnaire, Clinical Summary Score)
The clinical summary score from the Kansas City Cardiomyopathy Questionnaire: a validated, patient-reported measure of heart-failure symptoms and physical limitation. Scored 0–100, higher is better, and five points is the threshold for clinically meaningful. STEP-HFpEF reported 7.8 points on semaglutide against 2.6 on placebo — the primary endpoint behind the 2024 EMA and FDA filings in HFpEF with obesity.
- ATTAIN-1
Orforglipron's phase 3 in weight management, run in adults who had obesity but not diabetes: 72 weeks, N=3,127, across ten countries (NCT05869903). On the efficacy estimand the 17.2 mg arm lost 12.4% of body weight where placebo lost 0.9%.
- IWQOL-Lite-CT
Impact of Weight on Quality of Life, Lite Clinical Trials version: a 20-item patient-reported questionnaire validated for obesity drug trials, scored 0–100 with physical-function and psychosocial subdomains reported separately. Around 14.6 points is the meaningful-improvement threshold. STEP-1 and SURMOUNT-1 both posted large gains, which FDA used in weighing quality-of-life claims for Wegovy and Zepbound labeling.
- STEP-4 (withdrawal trial)
The withdrawal trial that settled whether a GLP-1 is a course or a commitment. All 803 participants reached 2.4 mg in a 20-week run-in, then were randomized 2:1 to continue or switch to placebo for 48 weeks. Continuers lost a further 7.9%; switchers regained 6.9% (Rubino 2021 JAMA, PMID 33755728). ⛔ Read it before signing a 12-month prepay, and before believing anyone selling a finite “program”.
- SYNERGY-NASH
Phase 2 of tirzepatide in adults with biopsy-confirmed MASH and significant fibrosis (Loomba 2024 NEJM, PMID 38856224). The endpoint was histologic — MASH resolution without worsening fibrosis at week 52, which requires a liver biopsy to score. 62% achieved it on 15 mg against 10% on placebo.
- LEADER (trial)
The first GLP-1 cardiovascular outcomes trial to show a MACE reduction: 9,340 adults with type 2 diabetes plus established CVD or high risk, liraglutide against placebo over a median 3.8 years (Marso 2016 NEJM, PMID 27295427). MACE HR 0.87, P=0.01. It established the class as cardioprotective before SUSTAIN-6 confirmed it.
- FLOW (trial)
The first GLP-1 trial built around the kidney rather than the waistline. Semaglutide 1 mg went up against placebo across 3,533 participants whose diabetes had already reached their kidneys (Perkovic 2024 NEJM, PMID 38785209). The kidney composite fell 24%, HR 0.76, and the study was halted early once the benefit was unmistakable. That is what drove the January 2025 Ozempic label expansion.
- SURMOUNT-5
The head-to-head everyone wanted: tirzepatide against semaglutide for weight management in non-diabetic adults with obesity (Aronne et al., NEJM 2025, PMID 40353578). Tirzepatide −20.2% against semaglutide −13.7% at 72 weeks, a 6.5-point gap. It is the strongest single argument for paying more for tirzepatide, and sellers of both cite it.
- SURMOUNT-2
Tirzepatide tested in adults who had both obesity and type 2 diabetes (Garvey et al., Lancet 2023). Tirzepatide 15 mg gave −14.7% body weight at 72 weeks against −3.2% on placebo, with HbA1c reductions beyond most diabetes-specific GLP-1 trials. It supported extending Zepbound labeling toward the T2D-with-obesity population.
- SURMOUNT-3
Tirzepatide started after a 12-week intensive lifestyle lead-in (Wadden et al., Nature Medicine 2023): a further −18.4% against −2.5% on placebo across the 72-week treatment phase. The useful reading is that the drug and the lifestyle work are additive, not alternatives — which is worth remembering when a seller bundles coaching and charges for it.
- SURPASS-2
Tirzepatide against semaglutide 1 mg in type 2 diabetes (Frías et al., NEJM 2021): HbA1c −2.30 points against −1.86, and body weight −11.2 kg against −5.7 kg over 40 weeks. The first major head-to-head between the two leaders, at a diabetes dose rather than a weight-management one.
- SUSTAIN-6
Cardiovascular outcomes for semaglutide in type 2 diabetes at high CV risk (Marso et al., NEJM 2016): a 26% relative reduction in three-point MACE. It confirmed what LEADER had signaled for the class.
- REWIND
Cardiovascular outcomes for dulaglutide in 9,901 adults with type 2 diabetes (Gerstein et al., Lancet 2019): MACE down 12% over a median 5.4 years. Notable for enrolling a majority who had NOT yet had a cardiovascular event — primary prevention, which is a harder result to get.
- PIONEER 6
Cardiovascular safety for oral semaglutide in type 2 diabetes at high CV risk (Husain et al., NEJM 2019), showing noninferiority for MACE. The point it settles: swallowing the drug does not cost you the cardiovascular safety profile of injecting it.
- STEP-HFpEF
Semaglutide 2.4 mg in heart failure with preserved ejection fraction plus obesity (Kosiborod et al., NEJM 2023), with substantial gains in KCCQ clinical summary score and six-minute walk distance. The first GLP-1 trial to show heart-failure-specific symptomatic benefit rather than event reduction alone.
- EXSCEL
Cardiovascular outcomes for once-weekly exenatide in 14,752 adults with type 2 diabetes (Holman et al., NEJM 2017), and the primary outcome was NEUTRAL. Exenatide did not significantly reduce MACE, which is why “GLP-1s protect the heart” is a claim about specific molecules rather than the class.
- ELIXA
Cardiovascular safety for lixisenatide after acute coronary syndrome in type 2 diabetes (Pfeffer et al., NEJM 2015): noninferior for MACE, not superior. The first GLP-1 cardiovascular outcomes trial completed under the FDA's post-2008 CV-safety guidance.
- AMPLITUDE-O
Cardiovascular outcomes for efpeglenatide in type 2 diabetes at high CV risk (Gerstein et al., NEJM 2021): a 27% relative reduction in three-point MACE. The drug was never marketed in the US, which is a reminder that trial success and availability are different questions.
- HARMONY OUTCOMES
Tested albiglutide for cardiovascular outcomes in an enrolled group of 9,463 people who had type 2 diabetes alongside existing cardiovascular disease (Hernandez et al., Lancet 2018). MACE came down 22%. GSK had withdrawn albiglutide from global markets a year before those results reached print, and the decision was commercial rather than clinical.
- SCALE Diabetes
Liraglutide 3.0 mg tested in adults who had both obesity and type 2 diabetes (Davies et al., JAMA 2015): −6.0% body weight at 56 weeks against −2.0% on placebo. It established the indication Saxenda still serves.
- STEP 2
Put semaglutide 2.4 mg to work in people carrying both excess weight and type 2 diabetes (Davies et al., Lancet 2021). Body weight came down 9.6% by week 68 against 3.4% on placebo, and HbA1c dropped 1.6 points. This is the trial Wegovy's use in a diabetic population rests on.
- SUMMIT
Tirzepatide in heart failure with preserved ejection fraction plus obesity (Packer et al., NEJM 2025), with substantial improvement in HFpEF-specific outcomes. The tirzepatide counterpart to STEP-HFpEF.
- SCALE Maintenance
Liraglutide 3.0 mg for holding weight loss after a low-calorie-diet run-in (Wadden et al., Int J Obes 2013): it preserved −6.2% of the run-in loss at 56 weeks against −0.2% on placebo. The maintenance case for a daily injectable, and an early sign of what STEP-4 later made unambiguous.
Side effects
What the FDA labels record as adverse events, each one tied back to the evidence it came from.
- Cholelithiasis
Gallstones, listed in Section 5 of every approved GLP-1 label. Wegovy reports 1.6% against 0.7% on placebo; Saxenda 2.2% against 0.8%. The He et al. 2022 meta-analysis pooled the class risk at RR 1.37 (95% CI 1.23–1.52). Rapid weight loss of any cause raises the risk, so this is not unique to the drugs.
- Ileus
Functional bowel obstruction, added to Section 6.2 of every GLP-1 label in 2023. The evidence pulls both ways: Sodhi's JAMA 2023 cohort found HR 4.22 for bowel obstruction, while the Ueda Scandinavian cohort in 2024 found HR 0.83. ⚠ Anyone quoting one of those without the other is arguing rather than informing.
- Telogen effluvium
Diffuse hair shedding set off by rapid weight loss or metabolic stress. Usually self-resolving over three to six months with enough protein and micronutrients. It is a weight-loss effect rather than a GLP-1 effect, which matters when a supplement is being sold to you as the fix.
- Ozempic face
The popular name for facial volume loss during rapid weight loss on a GLP-1. A 2025 Otolaryngology imaging cohort (PMID 40407186) put it at a median 9% midfacial volume loss, around 7% per 10 kg lost. It is fat leaving the face, not a drug toxicity — slower titration and a slower loss curve reduce it.
- Medullary thyroid carcinoma (MTC)
Medullary thyroid carcinoma, a rare tumor of the thyroid C-cells. The boxed warning every GLP-1 carries traces back to rodent studies, and no rise in human incidence has been shown. Anyone whose own history, or whose family history, includes MTC or MEN-2 should not take these drugs. A serious intake form asks about that. A careless one skips it.
- Lean mass loss
Muscle, bone and other non-fat tissue going along with the fat. The STEP-1 DEXA sub-analysis found roughly 39% of the weight lost was lean mass. Protein intake and resistance training are the mitigation, and they are the part no prescription covers.
Open the term page →Semaglutide and muscle mass: STEP DEXA sub-analyses →
- GLP-1-induced gastroparesis
Gastric emptying delayed enough to cause persistent nausea, vomiting or food sitting undigested. A 2023 JAMA case-control study (PMID 37335445) found a 3.7-fold increase in clinically diagnosed gastroparesis against bupropion-naltrexone. Risk climbs with higher doses, faster titration and pre-existing diabetic autonomic neuropathy; symptoms usually settle within four to eight weeks of reducing or stopping.
- Pancreatitis (acute)
Pancreatic inflammation, a labeled warning on every approved GLP-1. The mechanism looks indirect: gallstone-triggered duct obstruction rather than direct toxicity. Pooled FDA adverse-event data put incidence around 0.2–0.4% over typical treatment, against a background near 0.05% a year: elevated, still low in absolute terms. Prior pancreatitis, heavy alcohol use or symptomatic gallstones change that calculation.
- Pancreatic cancer risk (GLP-1 myth check)
An early worry from rodent studies showing acinar-cell hyperplasia. Large human cohorts and the SELECT trial (Lincoff 2023, PMID 37952131) have NOT shown a pancreatic-cancer signal across years of follow-up, and the 2024 FDA Drug Safety Communication confirmed no causal association is established. ⚠ The boxed warning covers thyroid C-cell tumors and acute pancreatitis — not this. It is worth knowing which warnings are real when someone is frightening you toward or away from a purchase.
Open the term page →SELECT trial deep-dive (long-term safety) →
- Lipohypertrophy
Thickened, swollen fat at a site injected over and over. The damaged tissue absorbs the drug erratically, so appetite suppression and results become unpredictable — people often read that as the drug failing. Rotate at least two inches between doses, cycling abdomen, thigh and upper arm across about eight weeks.
- Gastroparesis
Delayed gastric emptying bad enough to cause nausea, vomiting, early fullness and abdominal pain. GLP-1s slow emptying by design — useful for appetite, unpleasant when it tips over, and most likely to tip when the dose is escalated fast.
- Sarcopenia
Losing skeletal muscle mass and function. Any rapid weight loss takes muscle along with fat, whether from surgery, a GLP-1 or plain calorie restriction. The countermeasures are protein at 1.0–1.6 g/kg a day and resistance training while you are actively losing.
- Bone mineral density (BMD)
Bone strength in grams of mineral per square centimeter, measured by DXA. Losing more than 10% of body weight is associated with a mild reduction whatever caused the loss. Resistance training, enough calcium and vitamin D, and not running an extreme deficit all help hold it.
- Dumping syndrome
Nausea, cramping, diarrhea, dizziness and sweating from high-osmolar stomach contents hitting the small intestine too fast. Common after bariatric surgery, especially Roux-en-Y. ⚠ It is the OPPOSITE mechanism to GLP-1 gastroparesis, and the two get confused constantly.
- Intertrigo
Inflammation in skin folds (under the breasts, abdomen, thighs, armpits) from friction, moisture and secondary bacterial or fungal infection. Chronic intertrigo that has not responded to three months or more of medical therapy is the most-cited medical-necessity criterion for insurers covering panniculectomy and other post-weight-loss contouring.
Open the term page →Skin-removal cost + insurance qualifier →
Pharmacy and drug forms
Where a compounded drug parts company with an FDA-approved one, where 503A parts company with 503B, and which accreditation programs tell them apart.
- Compounded GLP-1
A GLP-1 prepared from bulk active ingredient by a 503A or 503B pharmacy rather than bought as the approved branded product. It is not an FDA-approved drug: no agency has reviewed that particular preparation for safety, effectiveness or manufacturing quality. This is what most sellers in this register are actually selling, and the legal ground under it narrowed sharply once the shortages closed in late 2024.
- 503A pharmacy
A state-licensed compounding pharmacy making preparations for named individual patients against a prescription. Held to USP <797> for sterile work, but its finished products are not FDA pre-approved. ⚠ If a seller will not name the 503A filling your vial, you cannot check its inspection history — and that is the single most common gap in this register.
- 503B outsourcing facility
An FDA-registered outsourcing facility that can compound in larger volumes without a patient-specific prescription. It is inspected by FDA and held to full cGMP, which is a materially higher bar than a 503A. Naming a 503B partner is one of the strongest disclosure signals a seller can offer.
- PCAB accreditation
Pharmacy Compounding Accreditation Board certification, run by ACHC: a voluntary third-party program covering sterility, potency verification and facility standards. Voluntary is the operative word: its absence is not a violation, and its presence is a real signal. ⚠ Verify any accreditation claim with the accreditor, not with the seller advertising it.
- USP <797>
The US Pharmacopeia chapter governing sterile compounding for humans: air quality, garbing, surface sampling and beyond-use dating. A 503A must demonstrate compliance to dispense sterile injectables such as compounded semaglutide. Inspections look at ISO Class 5 primary engineering controls, anteroom pressure differentials and operator media-fill testing.
- 503A vs 503B (pharmacy compounding)
The two FDA categories of sterile compounder, and the distinction worth learning before you buy. A 503A is state-licensed and compounds against a prescription naming you. A 503B registers voluntarily with FDA, can compound in bulk without prescriptions, and must meet full current Good Manufacturing Practice. Same molecule, different oversight, and sellers rarely volunteer which one fills their orders.
- Bacteriostatic water
Sterile water preserved with 0.9% benzyl alcohol, used to turn lyophilized powder back into an injectable solution. The preservative is what makes it safe to draw from the same vial repeatedly. ⚠ Being asked to mix your own medication means you have been handed a compounding step, and the strength you finish with depends entirely on how much water went in.
- Reconstitution
Turning a freeze-dried powder into a liquid you can inject by adding a measured volume of sterile or bacteriostatic water. The volume you add SETS the concentration, and the concentration sets how many syringe units your dose is. Getting it wrong scales the whole dose.
- U-100 insulin syringe
The syringe shipped with almost every compounded GLP-1 vial: 100 units to 1 mL, so one unit is always 0.01 mL. ⛔ U-40 syringes also exist, are used in veterinary insulin, and will deliver 2.5 times what you intend if you read one as U-100. Check the barrel.
- Vial versus pen
Approved GLP-1s come in pens that dial a dose in milligrams. Compounded GLP-1s usually come in vials you draw from with a syringe. That difference moves a measurement step from a factory to your kitchen, and it is why dosing errors are a compounded-market problem and essentially not a brand-market one.
- Sublingual and troche forms
Compounded preparations dissolved under the tongue rather than injected or swallowed. Marketed as needle-free. ⚠ No sublingual semaglutide or tirzepatide has an FDA-approved counterpart, so there is no bioavailability standard to compare against — the dose that reaches your bloodstream is not an established quantity.
- 503B bulk drug substances list
FDA's roster of active ingredients a 503B outsourcing facility is permitted to compound from once no shortage is on the books. A proposal dated 30 April 2026 would strike semaglutide, tirzepatide and liraglutide off it. Finalized, that shuts the last route by which these drugs could be compounded at scale.
- “Personalized” blend
A compounded product combining a GLP-1 with something else: B12, glycine, NAD+, an amino acid. ⛔ Marketed as tailored care; it is also a way to argue the preparation is not simply a copy of an approved drug. The additives have no trial evidence for weight loss at these doses, and they change what you are comparing on price.
Insurance and regulatory
The vocabulary of getting a claim paid, of FDA enforcement, and of what on-label and off-label really mean.
- FDA Warning Letter
FDA's formal notice that it considers a company in violation, demanding correction. We hold 158 of them and match each to a company by DOMAIN AND ADDRESS rather than by a name that merely looks similar. ⛔ A letter discloses a problem; it does not disqualify a seller and it is not a court finding. Only an enforcement action removes anyone from this register.
Open the term page →FDA warning letters to GLP-1 providers (live database) →
- Step therapy
The insurer requiring you to fail a cheaper or older drug first. For GLP-1s that usually means Contrave or Qsymia before Wegovy or Zepbound. A legitimate cost-control tool and, in practice, one of the biggest access barriers in the class.
Open the term page →GLP-1 insurance coverage: Medicare, Medicaid, commercial →
- Off-label use
Prescribing an approved drug outside its labeled condition or population. Legal, common, and Ozempic for weight loss is the textbook case. ⚠ Coverage frequently does not follow off-label use, so an off-label prescription and an affordable prescription are different things.
- FDA Drug Shortage List
FDA's public register of medicines in short supply. It is the hinge of this entire market: while semaglutide and tirzepatide sat on it, compounding them at scale was lawful under the shortage exemption. Both came off in late 2024, and the compounding that continues now rests on narrower ground.
Open the term page →Compounded GLP-1 price movement (12-month analysis) →
- Formulary tier
Where a drug sits in a plan's cost-sharing ladder. Tier 1 generic, Tier 2 preferred brand, Tier 3 non-preferred brand, Tier 4 specialty. Wegovy and Zepbound usually land in Tier 3 or 4 on commercial plans, so copays of $100–$500 a month are normal even AFTER approval, and some plans exclude them outright. No generic exists — semaglutide's US patent runs to 2032.
- PBM (Pharmacy Benefit Manager)
Pharmacy benefit manager: the middleman running the drug benefit for an insurer or employer: formulary design, prior-authorization rules, pharmacy network contracts, rebate deals with manufacturers. Express Scripts, CVS Caremark and OptumRx control roughly 80% of the US market, which makes three companies the effective gatekeepers of GLP-1 access.
- Copay accumulator
A plan design that stops manufacturer copay assistance from counting toward your deductible or out-of-pocket maximum. You still get the card's benefit while it lasts, then land back at full cost with the deductible untouched. Common on commercial high-deductible plans for exactly this class of drug.
- Specialty pharmacy
A pharmacy credentialed for high-cost, complex-handling drugs such as biologics, injectables and some GLP-1s. Many commercial plans route Wegovy, Zepbound and Mounjaro through a contracted specialty pharmacy rather than a retail counter. It adds monitoring requirements and can smooth prior authorization.
- Mail-order pharmacy
Fills by post, usually in 90-day supplies, generally through the plan's PBM and generally at a lower copay for maintenance drugs. GLP-1s shipped this way need refrigerated handling and a working cold chain — which is a question worth asking of any seller, not only an insurer.
- Quantity limit
A formulary cap on how much can be dispensed per fill, usually per 28 or 30 days. For GLP-1s it typically means one pen or one vial per 28 days regardless of what was prescribed, and it is one of the most common triggers for an appeal.
- Bridge therapy
A short-term prescription to keep someone going through a supply gap, such as moving a Wegovy patient to compounded semaglutide during a shortage, say, or to a lower Ozempic dose during a stockout. The intent is to bridge back. ⚠ In practice the bridge often becomes the destination, which is how a lot of people ended up on compounded product permanently.
- Patient assistance program (PAP)
A manufacturer program giving free or discounted medication to qualifying low-income patients without coverage. Novo Nordisk runs NovoCare and Eli Lilly runs LillyCares for their GLP-1 portfolios, each with income thresholds — commonly 400% of the federal poverty level or below — and recertification windows.
- Manufacturer coupon
A copay card from the drug maker that cuts what you pay at the counter. Novo Nordisk's Wegovy SavingsCard and Eli Lilly's Zepbound SavingsCard cap commercial-insurance copays at $0 or $25 for people who qualify. ⛔ Excluded for anyone on Medicare, Medicaid, VA or TRICARE, which is a much larger group than the advertising suggests.
- Deductible
What you pay yourself before the plan starts paying. High-deductible plans commonly run $1,500 to $8,000, which means a Wegovy patient can be paying the full cash price of roughly $1,000 a month until it is met — and that is the number worth comparing against a cash-pay seller, not the copay you reach afterwards.
- Coinsurance
The percentage share you pay after the deductible. On a 20% plan with a $1,000 monthly Wegovy bill, you pay $200 and the insurer pays $800. Different from a copay, which is a fixed amount, and it keeps applying until you hit the annual out-of-pocket maximum.
- Untitled letter
FDA's step below a warning letter: it cites violations without the formal warning-letter language or the corrective-action deadline. Lower severity, same underlying finding, and it does not appear in the warning-letter database — so a company with one can truthfully say it has never received a warning letter.
- Close-out letter
FDA's confirmation that a company has corrected what a warning letter cited. ⚠ We do not track close-outs, so the presence of a letter in this register tells you FDA said something — not how the company answered or whether the matter ended there. Ask the company; they will usually tell you, and how they answer is informative.
- Consent decree
A court-ordered settlement between a company and the government, typically imposing operating conditions and independent oversight. Far heavier than a warning letter: this is the instrument that actually stops a seller operating as it did.
- FTC action
Federal Trade Commission enforcement aimed at deceptive advertising or billing. Different agency from the FDA, different powers. Here it usually lands on negative-option billing, meaning a subscription you can sign up for in a minute and then cannot get out of.
- LegitScript certification
A commercial certification confirming an online pharmacy or telehealth business clears LegitScript's bar; the big ad platforms insist on it before they will run pharmaceutical advertising. ⚠ It is bought from a private company, not granted by a regulator. Check any claim of it against LegitScript's own directory rather than believing a badge on a website.
- State board of pharmacy
The state agency licensing pharmacies and pharmacists, and disciplining them. Licensure is state by state, which is why a pharmacy can be authorized to ship to one state and not the next — and why a seller's coverage map and its pharmacy's map do not always agree.
- Asynchronous intake
A written questionnaire reviewed by a clinician without a live conversation. Legal in many states and faster for everyone. ⚠ Some states require a synchronous visit before a first prescription, so a seller that is async everywhere else may add a call for you — and a seller that never does may not be following your state's rule.
- Enforcement discretion
FDA choosing not to act against conduct it could act against. It is a decision, not a permission, and it can be withdrawn, which is exactly what happened here: discretion for compounded semaglutide ended 22 April 2025 for 503A pharmacies and 22 May 2025 for 503B facilities.
- “Research chemical” / not for human consumption
Peptides sold with a label saying they are not for human use, a disclaimer meant to sidestep drug regulation while the marketing addresses people who plainly intend to inject them. ⛔ There is no prescriber, no pharmacy, no accountable party and no way to establish what is in the vial. This register does not list these sellers, and no price comparison here should be read as covering them.
Open the term page →Why this market exists and what it costs →
Dosing
The practical ones: titration, half-life, washout, and what a missed dose does.
- Titration
Stepping the dose up gradually so the side effects stay tolerable. Tirzepatide's standard ladder moves every four weeks: 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg. Going slower blunts nausea. ⚠ It also matters commercially: a seller charging by dose gets more expensive every time you climb a rung, and a flat-price seller does not.
- Half-life
How long it takes plasma concentration to halve. Semaglutide about 7 days, tirzepatide about 5, liraglutide about 13 hours, orforglipron about 36. It decides weekly against daily dosing, and it decides how long a drug lingers after you stop — which is the number that matters for washout and pregnancy planning.
- Washout period
The waiting gap between coming off one GLP-1 and starting the next, or before trying for a baby. Wegovy's label puts that second figure at two months ahead of any planned pregnancy, a direct consequence of how long semaglutide lingers in the body.
- Missed dose
A weekly injection that got skipped. With semaglutide and tirzepatide the rule is five days: inside that window, take it late. Past it, leave that dose alone and pick the schedule back up as normal. Never stack two to catch up.
Buying and billing
How sellers price a month: billing cycles, first-month rates, prepay plans and what a membership fee covers.
- Billing cycle
How often a seller actually charges you, which is not always monthly. A 28-day cycle bills 13 times in a calendar year, not 12, so “$149 a month” on a 28-day cycle costs $1,937 a year rather than $1,788. ⛔ The cycle is usually disclosed in the terms rather than on the price card. It is the single most common way a headline price understates the real one.
- Cash price
What you pay with no insurance involved. It is the only figure that compares cleanly across this market, because insured costs depend on your plan, your deductible and your employer. Every price in this register is a cash price unless the row says otherwise.
- First-month rate
An introductory price that applies once and then lifts. “From $49” is very often this. ⛔ We do not record a first-month rate as the monthly price, because the number that matters is the one you pay in month three. Where a seller publishes both, this register carries the standing rate and notes the intro.
- Anchor price
The struck-through figure beside the price you are offered. It sets an expectation rather than describing a transaction, and nobody is charged it. We record it as an anchor, never as a discount, and never as evidence the offered price is good.
- Dose-based pricing
A plan whose price climbs as your dose is titrated up. The advertised figure is the starting dose, and the cost of a full course is a different number entirely. The opposite arrangement is flat pricing. Which one a seller uses matters more to a year's spend than the headline rate does.
- Flat pricing
One price at every dose, so titrating up costs nothing extra. Genuinely valuable and worth verifying rather than assuming: “all doses included” sometimes means all doses up to a cap, with the cap in the terms.
- Prepay plan
Paying for three, six or twelve months up front for a lower monthly equivalent. The “as low as” price on most pricing pages is a twelve-month prepay rate. ⚠ Weigh it against STEP-4: this is chronic therapy, so a long commitment is not automatically wrong — but it is a bet on the seller, the pharmacy and the price all still suiting you in month eleven.
Open the term page →How commitment terms distort a price comparison →
- Membership fee
A separate recurring charge for access, consultation or “the program”, on top of the medication. ⛔ A membership fee is not a medication price, and this register does not record one as though it were. When a seller quotes a low figure, the question is what it buys.
- What's included
Whether the monthly figure covers the medication, the consultation, shipping, labs and coaching, or only some of those. Two sellers at the same price can be offering materially different things, and the gap is usually shipping and the consult. Every review here records it field by field.
Patient experience
Words you meet in patient communities rather than on a label. Plateau, microdosing, switching.
- Plateau
Weight loss stalling after months of progress: metabolic adaptation, habits drifting back, or simply reaching the dose ceiling. Often moves again with re-titration, a dietary review or resistance training. ⚠ It is also the moment sellers pitch an upgrade tier, so it is worth knowing the stall is expected rather than a product failure.
- Microdosing
Off-label use of doses below the approved range, to soften side effects or stretch a vial. Evidence is thin: the published randomized data were all run at approved doses. It is now sold as its own product tier, and whether it is cheaper than a standard dose depends far more on the commitment term than on the dose.
- Switching GLP-1s
Moving between GLP-1s, most often semaglutide to tirzepatide. Expect to re-titrate; both the old drug's washout and the new drug's ladder apply. A seller who switches you without restarting titration is doing you no favors.
- Rebound weight gain
Regain after stopping. The STEP-1 withdrawal extension (Wilding 2022, Diabetes Obes Metab, PMID 35441470) found people who came off semaglutide 2.4 mg after 68 weeks put back two-thirds of the lost weight within a year, with pre-treatment metabolic risk markers returning too. This is the evidence that made the class chronic therapy rather than a course of treatment.
Open the term page →STEP-1 withdrawal extension on our top studies list →
- GLP-1 + anesthesia (preoperative)
The American Society of Anesthesiologists' 2023 guidance recommended holding daily GLP-1s for a day and weekly ones for a week before anesthesia, because delayed gastric emptying raises aspiration risk. The 2024 update is less rigid — no strict hold required if NPO for 18 hours or more and clinical judgment supports proceeding. Endoscopy patients on a GLP-1 show roughly 6× the rate of retained gastric contents. ⚠ Tell the anesthetist, every time.
- Subcutaneous (subq) injection
Delivered into the layer of fat beneath the skin rather than into muscle. Everything injectable in this class is given that way, Wegovy and Ozempic through Zepbound, Mounjaro, Saxenda, Victoza and Trulicity. Usual spots are the belly (staying a couple of inches clear of the navel), the thigh at the front, or the upper arm at the back, and you move the spot each week.
- GLP-1 in pregnancy
Every approved GLP-1 carries a pregnancy precaution, with discontinuation recommended at least two months ahead of a planned conception for semaglutide given its half-life. Animal studies show developmental toxicity at human-equivalent doses; there are no randomized human data and observational registries are still accumulating. Reliable contraception matters for anyone of reproductive age. ⚠ Accidental early exposure is not in itself an indication for termination — that is a conversation for a maternal-fetal medicine specialist.
- Intensive Behavioral Therapy (IBT)
Intensive behavioral therapy: structured weight-management counseling from a dietitian or qualified clinician, typically around 30 visits over 12–14 months, targeting 1,000–1,500 kcal a day and at least 200 minutes of activity a week. Some insurers require it before authorizing Wegovy or Zepbound. STEP-3 and SURMOUNT-3 both showed it is additive to the drug rather than redundant with it.
Where the evidence lives
Treat this page as the index. The working detail sits in the research articles, the tools and the provider reviews:
- Research articles — 100+ deep dives, every one cited to PubMed.
- Tools and calculators — 38 of them, a titration planner and a washout calculator among them, plus a drug interaction checker and a missed-dose guide.
- Compare providers — one filterable table covering 570+ GLP-1 telehealth providers.
- FDA warning letters database — every warning letter the FDA has sent a compounded GLP-1 seller or pharmacy, refreshed every two weeks.