How this works
The math
How the arithmetic works
strength in mg/mL = label figure ÷ 0.5mL = dose in mg ÷ strength in mg/mLunits = mL × 100 (U-100 only)For example, 10 mg per 0.5 mL is 20 mg/mL, and 7.5 mg is 0.375 mL, or 37.5 units. It isn’t rounded to 38: that’s about 1% more than the dose, and the difference is for your pharmacist to settle. A dose equal to the label figure is always 0.5 mL, or 50 units.
What the label shows
- The convention
- A label that prints “10 mg/0.5 mL” means 10 mg in half a milliliter, so the strength is 20 mg/mL. It’s a way of printing the figure, and it doesn’t tell you who made the vial or how.
- FDA-approved vials
- Zepbound’s and Mounjaro’s single-dose vials print mg per 0.5 mL, and each is used whole: 0.5 mL, or 50 units.12 Their multi-dose vials are different: 2.4 mL, with 0.6 mL doses.12
- Compounded vials
- FDA says they aren’t FDA approved, and that their concentrations and instructions vary.34 The label on your vial, and the pharmacy that filled it, come before this page.
- Drawing part of a vial
- No label describes it for a single-dose vial. FDA’s reports describe errors when people measured doses from vials themselves.3
- This page
- It doesn’t name, recommend or compare pharmacies or products. If your label prints anything else, use Units, mL and mg, where you type the label as printed.
Before you act on this
FDA’s reports include people drawing five to 20 times more than the intended dose from multiple-dose vials, and health care providers miscalculating doses when converting mg to units or mL.3 Ask your pharmacist to check your numbers.
Took more than you were prescribed? Call your prescriber or pharmacist now. In the US, Poison Help is 1-800-222-1222. Severe vomiting, severe nausea or signs of low blood sugar need urgent care.
Something went wrong, or a vial looks or acts wrong? Tell your prescriber. In the US, you can also report it to FDA’s MedWatch program.4
Always follow your doctor’s or prescriber’s advice and guidance. Talk to your prescriber before changing your dose.
Read this first
This only works if your label prints 0.5 mL
- Read your label before you type anything. If “0.5 mL” isn’t printed right beside the figure, this result will be wrong. A figure read per 1 mL instead is off by two times.
- This is a labeling convention, not a standard. FDA says compounded concentrations vary, and one compounder may offer several.3 Compounded drugs aren’t FDA approved or reviewed for safety, effectiveness or quality.4
- Zepbound’s and Mounjaro’s vials that print mg per 0.5 mL are single-dose: the whole vial, one time.12 No label describes drawing part of one.
For information only, not medical advice. Verify results with your healthcare provider; Onederland accepts no liability for use of these tools.
- Runs on this device. Nothing you type is sent anywhere.
- Every figure names its source, below.
- Education, not medical advice. Your prescriber comes first.
Sources
Sources
- Zepbound (tirzepatide) injection, US prescribing information, revised 08/2026. accessdata.fda.gov
- Mounjaro (tirzepatide) injection, US prescribing information, revised 08/2026. accessdata.fda.gov
- FDA: dosing errors with compounded injectable semaglutide, July 26, 2024. fda.gov
- FDA: concerns with unapproved GLP-1 medicines, October 1, 2026. fda.gov
Label sources last checked on October 30, 2026. Onederland summarizes them; your prescriber and the full prescribing information come first.
