Tirzepatide Dose Calculator: Convert mg to Units and Check Syringe Fit
A tirzepatide dose calculator turns a prescribed milligram dose into syringe units for a compounded vial. At 10 mg/mL, 2.5 mg is 25 units and 7.5 mg is 75 units on a U-100 syringe, while 12.5 mg would need 125 units, more than a 1 mL barrel holds. The Zepbound label describes its single-dose vials as a 0.5 mL solution drawn by volume, with no mixing step.[2]
Tirzepatide dose calculator
Arithmetic only. This calculator does not recommend a dose. Follow your prescriber's instructions.
How many units is 2.5 mg of tirzepatide?
The unit count depends on the concentration of the vial. On a U-100 syringe there are 100 units in 1 mL,[7] so units equal the dose divided by the concentration, times 100. At 10 mg/mL, a 2.5 mg dose is 0.25 mL, or 25 units. At 5 mg/mL the same dose is 0.5 mL, or 50 units. At 20 mg/mL it is 0.125 mL, or 12.5 units, which falls between the printed lines of a standard syringe. Because tirzepatide labels list doses from 2.5 mg up to 15 mg,[1] the volumes are larger than for many other peptides, and the barrel size matters more than tiny draws do. Enter the vial milligrams, the water or liquid volume, and the dose your prescriber set. Then compare the concentration the calculator shows with the label on your vial. If they differ, stop and ask your pharmacist before you draw.
Do Mounjaro and Zepbound need a dose calculator?
No. The Zepbound label lists single-dose vials and pens in strengths of 2.5, 5, 7.5, 10, 12.5, or 15 mg per 0.5 mL, and it describes each single-dose vial as a 0.5 mL solution whose instructions go from opening the vial to drawing 0.5 mL, with no mixing step.[2] The Mounjaro label lists single-dose pens and vials in the same six strengths per 0.5 mL.[1] With these products the whole container is one dose, so there is no concentration to work out and no units to read. The Zepbound label also lists a 2.4 mL multi-dose vial that holds four doses, so read your own label. This calculator is for a tirzepatide vial that a pharmacy has prepared at its own concentration and that you draw with an insulin syringe. In that case the concentration printed on the label decides the units, and it can differ from one pharmacy to another. If unsure which product you hold, ask your pharmacist.
What happens when a tirzepatide dose will not fit in one syringe?
A syringe barrel holds a fixed volume, and its capacity in units is the barrel volume times the units per milliliter. A 1 mL U-100 barrel holds 100 units, and a 0.5 mL U-100 barrel holds 50.[7] Suppose a vial is 10 mg/mL and the prescribed dose is 12.5 mg. The draw is 1.25 mL, or 125 units, which is more than a 1 mL barrel holds. The calculator reports this overflow. The volume depends on the concentration: at 20 mg/mL the same 12.5 mg is 0.625 mL, or 62.5 units, which fits in the barrel. The calculator does not say what to do about an overflow, because that depends on the product and the person. Your prescriber or pharmacist can tell you what applies to the vial you hold. If both problems apply, the overflow warning is the one shown, because it is the more serious.
What if a tirzepatide dose falls between unit lines?
Take a vial at 20 mg/mL and a 12.5 mg dose. The volume is 0.625 mL, which is 62.5 units on a U-100 syringe. A standard syringe has whole-unit lines, so you cannot draw half a line accurately. Rounding up to 63 units delivers 63 divided by 100, times 20, which is 12.6 mg, instead of 12.5 mg. The difference is small here, but it grows with concentration, because each unit at 20 mg/mL holds 0.2 mg. A different concentration would change where the dose falls. At 10 mg/mL the same 12.5 mg is 125 units, which is more than one barrel holds, so concentration trades one problem for another.[7] The calculator shows the rounded draw and the dose it delivers. Whether any rounding is acceptable is a question for your prescriber or pharmacist.
| Dose | 5 mg/mL | 10 mg/mL | 20 mg/mL |
|---|---|---|---|
| 2.5 mg | 50 units | 25 units | 12.5 units (between lines) |
| 5 mg | 100 units | 50 units | 25 units |
| 7.5 mg | 150 units (over) | 75 units | 37.5 units (between lines) |
| 10 mg | 200 units (over) | 100 units | 50 units |
| 12.5 mg | 250 units (over) | 125 units (over) | 62.5 units (between lines) |
| 15 mg | 300 units (over) | 150 units (over) | 75 units |
What is the FDA-label dose schedule for tirzepatide?
The Mounjaro label says the recommended starting dose is 2.5 mg injected under the skin once weekly, with increases in 2.5 mg steps after at least 4 weeks on the current dose, up to a maximum of 15 mg once weekly for adults.[1] The Zepbound label starts at 2.5 mg once weekly for 4 weeks, then raises the dose to 5 mg, and it allows 2.5 mg steps after at least 4 weeks. For weight reduction its maintenance doses are 5, 10, or 15 mg once weekly, and the maximum for all indications is 15 mg.[2] These are label facts, shown so you can see what each milligram dose becomes in units at your concentration. They are not a recommendation, and the dose and pace for you are set by your prescriber. The table lists the steps side by side for reference.
| Item | Mounjaro label | Zepbound label |
|---|---|---|
| Start | 2.5 mg weekly | 2.5 mg weekly for 4 weeks |
| Next step | Up in 2.5 mg steps after at least 4 weeks | 5 mg, then 2.5 mg steps after at least 4 weeks |
| Maximum | 15 mg weekly (adults) | 15 mg weekly |
| Missed dose | Within 4 days (96 hours) | Within 4 days (96 hours) |
What does the FDA say about compounded tirzepatide in 2026?
As of October 2026, the FDA states that compounded drugs are not FDA approved, so the agency does not review them for safety, effectiveness, or quality before they are marketed.[4] It determined that the tirzepatide injection shortage was resolved on December 19, 2024. Once a shortage ends, the drug counts as commercially available, and compounders can no longer regularly make copies unless they meet specific exemptions, such as a prescriber documenting a significant difference for an individual patient.[5] On April 30, 2026, the FDA proposed to exclude semaglutide, tirzepatide, and liraglutide from the 503B bulks list. Comments were due June 29, 2026, and the agency said it would consider them before a final decision, so this remains a proposal and not a final rule.[6] Rules change, so check the FDA pages for the latest status. Your prescriber and pharmacist can tell you what applies to the product you hold.
How is tirzepatide different from semaglutide for dosing math?
The arithmetic is identical: dose divided by concentration gives milliliters, and milliliters times the units per milliliter gives units. What differs is the size of the numbers. The Mounjaro label lists doses in 2.5 mg steps up to 15 mg,[1] while the Ozempic label lists a maximum of 2 mg.[8] A tirzepatide dose is therefore often several milligrams, so the volume to draw is larger. The common failure shifts from reading a tiny mark on the barrel to running out of barrel. A 7.5 mg dose at 5 mg/mL needs 150 units, which a 1 mL U-100 syringe cannot hold.[7] The error the FDA documented with compounded semaglutide, drawing 50 units instead of 5, came from unit and milliliter confusion, and the same confusion can affect any vial.[3] Check the scale on the syringe and the concentration on the vial first.
Frequently asked questions
Is 50 units of tirzepatide 5 mg?
Only at 10 mg/mL on a U-100 syringe. At 5 mg/mL, 50 units is 2.5 mg, and at 20 mg/mL it is 10 mg. Units depend on concentration, so read the milligrams per milliliter from your own vial label.
Can I split a dose across two syringes?
The calculator flags when a dose needs more units than the barrel holds, but it does not say how to handle that. Whether a dose can be split across syringes depends on the product and the person, so ask your prescriber or pharmacist.
Why is my result a half unit?
The dose and concentration do not divide to a whole line. For example, 12.5 mg at 20 mg/mL is 62.5 units. The calculator shows the rounded draw and the dose it delivers so you can see the difference.
Does this work for Zepbound vials?
The Zepbound label describes its single-dose vial as a 0.5 mL solution, and its instructions go straight to drawing 0.5 mL with no mixing step, so there is nothing to calculate. The label also lists a multi-dose vial dosed in milliliters. This tool is for vials prepared by a pharmacy at its own concentration.
What if I miss a dose?
The Mounjaro and Zepbound labels say to give a missed dose as soon as possible within 4 days (96 hours) after the missed dose. Beyond that, ask your prescriber what to do before the next dose.
Does PepTrac recommend a tirzepatide dose?
No. PepTrac is an educational record-keeping app and does not give medical advice, choose doses, or sell any peptide. You enter the dose your prescriber set, and the app converts and logs it.
Sources
- DailyMed, National Library of Medicine (Eli Lilly). Mounjaro (tirzepatide) injection prescribing information. Accessed October 3, 2026.
- DailyMed, National Library of Medicine (Eli Lilly). Zepbound (tirzepatide) injection prescribing information. Accessed October 3, 2026.
- U.S. Food and Drug Administration. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products. Accessed October 3, 2026.
- U.S. Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. Accessed October 3, 2026.
- U.S. Food and Drug Administration. FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize. Accessed October 3, 2026.
- U.S. Food and Drug Administration. FDA proposes to exclude semaglutide, tirzepatide and liraglutide from 503B bulks list. Accessed October 3, 2026.
- MedlinePlus, National Library of Medicine. Giving an Insulin Injection. Accessed October 3, 2026.
- DailyMed, National Library of Medicine (Novo Nordisk). Ozempic (semaglutide) injection prescribing information. Accessed October 3, 2026.
Written and maintained by the team that builds PepTrac. Every calculator on this site runs the same tested math as the app. Read how we research, cite, and update pages in our editorial policy.
