How this works
The math
How it works
Milligrams are how much medicine you take. Milliliters are how much liquid holds it. Units are the marks on an insulin-style syringe, and on a U-100 syringe 100 units is 1 mL.1
mL = dose in mg ÷ strength in mg/mLunits = mL × 100 (U-100 only)mg = units ÷ 100 × strength in mg/mLWhat the label shows
The Zepbound label is a worked example. Its single-dose vial is 5 mg in 0.5 mL, so the dose is 0.5 mL, the 50 mark on a U-100 syringe. Its multi-dose vial holds 10 mg in 2.4 mL, and a 2.5 mg dose is 0.6 mL, the 60 mark.2
When a label prints a rounded strength such as 4.17 mg/mL, use the mg and mL it also prints. The rounded figure gives 59.95 units where the exact one gives 60.
In the FDA dosing-error example, 5 units on a U-100 syringe is 0.05 mL. At a strength of 5 mg/mL, 0.25 mg is 5 units, while 25 units is 1.25 mg. Drawing 50 units instead of 5 units means drawing 10 times the intended amount.1
Reverse example: 25 U-100 units is 0.25 mL. At 20 mg/mL, that contains 5 mg. The units alone cannot identify the mg.
Before you act on this
FDA has reports of people taking five to 20 times their intended dose after drawing the wrong amount from a compounded semaglutide vial, some needing hospital care. Several people meant to draw 5 units and drew 50.1 Say your number out loud and look at the syringe before you inject.
If you took more than you were prescribed, call your prescriber or pharmacist now. In the US, Poison Help is 1-800-222-1222. Outside the US, call your local emergency number or poison center. Severe vomiting, severe nausea or signs of low blood sugar need urgent care.
Always follow your doctor’s or prescriber’s advice and guidance. Talk to your prescriber before changing your dose.
For information only, not medical advice. Verify results with your healthcare provider; Onederland accepts no liability for use of these tools.
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- Every figure names its source, below.
- Education, not medical advice. Your prescriber comes first.
Sources
Sources
- FDA: dosing errors with compounded injectable semaglutide, July 26, 2024. fda.gov
- Zepbound (tirzepatide) injection, US prescribing information, revised 08/2026. accessdata.fda.gov
Label sources last checked on October 30, 2026. Onederland summarizes them; your prescriber and the full prescribing information come first.
