Vial labels · concentration · units · beyond-use date

What every field on your vial means

A first vial of compounded semaglutide or tirzepatide arrives carrying half a dozen numbers, and misreading one of them is not a harmless mistake. Tap any field on the label below and it explains itself in plain words. Then put your own vial's numbers into the calculator and it returns the mark to draw to on a U-100 insulin syringe.

Read your label first

A compounded GLP-1 is not an FDA-approved product, and of everything patients report getting wrong, one thing dominates: reading syringe units as milligrams. Tap any part of the label below and it explains itself. This is educational, and it stands behind your pharmacy's printed instructions rather than in front of them.

Your vial label — tap a field

Prescribed dose → units

What it is: The week's dose in milligrams, beside the units that come to on a U-100 insulin syringe. One mL is 100 units, so a single unit is 0.01 mL.

Why it matters: ⚠️ More reports come in about this than anything else: units read as though they were milligrams. 12.5 units is not 12.5 mg. Convert every time, using the concentration on your own vial — the calculator below will do it.

Decode your own vial

Type in what your own label says, and the concentration, the mark to draw to, and the number of doses in the vial all follow.

DrugVial peptide content (mg)Bacteriostatic water added (mL)Your prescribed dose (mg)

Concentration

2.00 mg/mL

Draw to this mark

12.5 units

Doses per vial

Take the vial label and the concentration to your prescribing clinician and your compounding pharmacy, every time. What this calculator gives you is educational; the dosing instructions that come with the medication are what govern.
Stick to compounding pharmacies that are state-regulated or PCAB-accredited. FDA enforcement discretion for compounded GLP-1s has since lapsed — tirzepatide in February 2025, semaglutide in April 2025 — so confirm where your pharmacy stands legally.

12.5 units ≠ 0.25 mg. You draw to the 12.5-unit mark on a U-100 insulin syringe to deliver your 0.25 mg dose. Always confirm against your pharmacy's instructions.

Unsure whether the vial came from somewhere legitimate?

Our register covers licensed GLP-1 sellers, checked by us, and none of it requires insurance.

See vetted compounded GLP-1 providers →

The mistake that puts people in the emergency room

One error accounts for more harm here than all the others together: reading a unit as a milligram. Your prescription is written in milligrams — 0.25 mg, say. The marks on a U-100 insulin syringe are not milligrams of drug at all; they measure volume. With 100 units to the milliliter, that 0.25 mg dose out of a 2 mg/mL vial comes to 12.5 units — not 25, and certainly not a quarter of the barrel. The ISMP put out an advisory on this exact confusion in December 2024, and the FDA has taken hundreds of dosing-error reports since, some of them overdoses of 5 to 20 times the intended amount [1][2].

Taking the label apart, field by field

Vial strength (mg) counts everything in the vial, which is not what you are taking this week. A 5 mg vial is normally many weeks’ worth.
Concentration (mg/mL) is the vial strength divided by the bacteriostatic water that went in. Everything else depends on it.
Units to draw is your dose divided by that concentration, times 100 — done for you by the calculator above.
Beyond-use date [3] is the day the vial is thrown out. Go by what is printed on your label, not by any general rule.
Pharmacy and lot ought to name a licensed 503A, or a 503B registered with the FDA, alongside your batch. A label carrying neither a pharmacy nor a patient name is a warning sign [4].

Before you draw any dose

A compounded GLP-1 is not an FDA-approved product, and this page is educational: it stands behind your pharmacy's printed instructions and your prescriber's directions, never in front of them. Check the concentration on the vial in your hand every time, have your dose confirmed by the person who prescribed it, and do not use a vial once its beyond-use date has passed. Anyone with medullary thyroid carcinoma or MEN 2 in their own history or their family's should not be taking these drugs at all.

References

1.Institute for Safe Medication Practices (ISMP). Compounded GLP-1s require extra vigilance — units-vs-milligrams dosing errors (December 2024 advisory). ISMP / ECRI. 2024. https://home.ecri.org/blogs/ismp-news/compounded-glp-1s-require-extra-vigilance
2.U.S. Food and Drug Administration. FDA's concerns with unapproved GLP-1 drugs used for weight loss — dosing-error reports and compounded-product warnings. FDA.gov — Postmarket Drug Safety Information. 2025. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
3.United States Pharmacopeia. USP <797> Pharmaceutical Compounding — Sterile Preparations (2023 revision; beyond-use dating). USP General Chapters. 2023. https://www.usp.org/compounding/general-chapter-797
4.Pharmacy Compounding Accreditation Board (PCAB). PCAB Accreditation Standards for Sterile Compounding Pharmacies — how to verify a compounding pharmacy. Accreditation Commission for Health Care. 2024. https://www.achc.org/pharmacy/pcab/

Related tools and guides

GLP-1 reconstitution calculator — full BAC-water + concentration + units math with safety guards
What's in the box? GLP-1 starter kit decoded — every item in your kit, explained
Is identification required to buy a GLP-1 online? — how legitimate platforms verify you
Compounded GLP-1 reconstitution & mixing guide — step-by-step walkthrough
Is compounded semaglutide still available in 2026?
Pharmacy legitimacy lookup — vet the pharmacy that filled your vial
Best compounded semaglutide providers and where to buy semaglutide safely

Ready to start? GLP-1 providers we have vetted

Telehealth providers, vetted by us, prescribing GLP-1 online.

Vetted by our editors · no insurance required

Some of the links on this page earn us money. If you sign up with a provider after following one, that provider may pay GLP Watchdog a commission. Learn more

8.4