Dosage calculator

GLP-1 Split Dose Calculator

Nausea and GI side effects ease for some people when the weekly GLP-1 dose is taken as two or three smaller injections instead of one. Give this calculator your dose and it returns what each injection works out to in milligrams, syringe units and milliliters, together with a schedule to put them on.

Split dosing is off-label. One injection a week is what the FDA approved, for tirzepatide and for semaglutide alike. Take any change of schedule to your prescriber first.

Select your drug

Total weekly dose (mg)

mg/week

Injections per week

Vial concentration (mg/mL)

Read the concentration off your vial label.

Per injection (2× per week)

1.2mg

Syringe units per injection

48units

Volume per injection

0.480mL

Suggested schedule

Monday + Thursday (every 3-4 days)

Space injections as evenly as possible. The exact days don't matter — consistency does.

Total weekly verification

1.2 mg × 2 injections = 2.40 mg/week (unchanged)

Why split dosing?

The FDA-approved regimen for both semaglutide (Wegovy/Ozempic) and tirzepatide (Zepbound/Mounjaro) is a single subcutaneous injection once per week [2, 4]. However, some patients — especially during the early titration weeks — experience significant nausea, vomiting, or GI distress that limits their ability to tolerate the full dose at once.

Prescribers in the compounded GLP-1 market sometimes recommend splitting the weekly dose into 2 or 3 smaller injections, spaced evenly across the week. The total weekly milligrams remain the same; only the per-injection amount changes.

This is off-label use. There are no published clinical trials specifically studying split-dose GLP-1 regimens for weight management. The pharmacokinetics of semaglutide (half-life ~7 days) and tirzepatide (half-life ~5 days) support once-weekly dosing, and splitting may alter the plasma concentration profile. Always discuss split dosing with your prescriber before changing your injection schedule.

The math

Nothing but division. Take a weekly dose of W mg across N injections and:

per-injection mg = W ÷ N

The U-100 standard then gets you to syringe units [1]:

per-injection units = (per-injection mg × 100) ÷ concentration (mg/mL)

Worked through: a 2.4 mg/week semaglutide dose, 2 injections, vial concentration 5 mg/mL.

1.2 mg per injection × 100 ÷ 5 = 24 units per injection

Scheduling

Aim for even spacing across the week:

2 injections/week: Monday + Thursday (every 3-4 days) or any two days ~3.5 days apart.
3 injections/week: Monday + Wednesday + Friday (every 2-3 days).

Which days you pick matters less than picking days you will actually keep to. Choose them once and hold the pattern.

Important safety disclaimer

Split dosing is off-label for all GLP-1 receptor agonist approved for weight management. What this page does is arithmetic, nothing more — it is not medical advice, and no injection schedule should change without your prescriber in the conversation. GLP Watchdog offers no diagnosis, treatment recommendation or medical advice of any kind.

References

1.Becton, Dickinson and Company (BD). BD Ultra-Fine Insulin Syringes — Product Specifications and U-100 Standard. BD Diabetes Care Product Documentation. 2024. https://www.bd.com/en-us/products/diabetes/diabetes-injection/insulin-syringes
2.Novo Nordisk Inc. WEGOVY (semaglutide) injection — US Prescribing Information. FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/215256s026lbl.pdf
3.Novo Nordisk Inc. OZEMPIC (semaglutide) injection — US Prescribing Information. FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/209637s035,209637s037lbl.pdf
4.Eli Lilly and Company. ZEPBOUND (tirzepatide) injection — US Prescribing Information. FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/217806s002lbl.pdf
5.Eli Lilly and Company. MOUNJARO (tirzepatide) injection — US Prescribing Information. FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/215866s039lbl.pdf
6.U.S. Food and Drug Administration. Compounded Drug Products — 503A and 503B Outsourcing Facility Information for Patients. FDA Drug Compounding Resources. 2024. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers

Related tools and research

GLP-1 unit ↔ mg converter — move between milligrams and syringe units at whatever concentration you have.
GLP-1 reverse dose calculator — work back from syringe units to the mg dose.
GLP-1 vial transition calculator — redo the syringe-unit math after a change of vial concentration.
GLP-1 dose plotter — chart plasma concentration through every titration step.
GLP-1 washout calculator — work out how long the drug lingers once you stop.
PCAB accreditation investigation — sizing up whoever is filling your prescription.
Split dosing: what the evidence really shows — the evidence review this calculator sits on, and the documented safety risk that deserves more weight than the efficacy argument does.

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