Tirzepatide Dosing in Units: Master Chart for All 4 Vial Sizes

Tirzepatide Dosing in Units by Vial Size (Master Table)

Below is the complete lookup: 4 standard compounded vial sizes (rows) by 6 titration doses (columns). Find your vial on the left and read across for every dose. Values flagged with an asterisk exceed a standard 1mL U-100 syringe and need a 1.5mL syringe or a split injection. Cells marked "n/a" mean the requested dose is larger than the vial's total mg, so it cannot be drawn from that vial at all.

If you only need the starting-dose answer, the 2.5mg starting dose conversion article focuses on that single step in depth.

* Dose is physically available from this vial but the IU draw exceeds a standard 1mL U-100 syringe (100 IU max). Use a 1.5mL syringe or split the dose into two separate draws. "n/a" = the requested dose exceeds the total mg in the vial, so it cannot be drawn from this vial size at all.

How to Read This Table

Two worked examples confirm the math:

• 2.5mg at 5mg/mL: (2.5 / 5) x 100 = 50 IU. Draw to the 50-unit line, exactly halfway up the barrel.
• 10mg at 10mg/mL: (10 / 10) x 100 = 100 IU. Draw to the 100-unit line, a full standard syringe.

For any non-standard vial or BAC water volume, the free tirzepatide calculator returns the exact draw without manual math, or jump straight to the tirzepatide dose-to-units calculator to convert a single mg dose to syringe units.

Why Tirzepatide Dosing in Units Depends on Vial Concentration

The IU marks on a U-100 insulin syringe measure volume, not mass. Each unit represents 0.01mL of liquid; 100 units fills the standard 1mL barrel. Those marks were designed for insulin, where 1 IU has a fixed mass meaning. Tirzepatide is not insulin, so "units" carry no inherent mg value. The same syringe mark holds different mg of tirzepatide depending on how concentrated your solution is.

This is why online answers conflict. A clinic using 5mg/mL says "50 units for 2.5mg." A pharmacy using 10mg/mL says "25 units for 2.5mg." A specialty compounder using 25mg/mL says "10 units for 2.5mg." All three are correct for their concentration. None are correct for yours unless your vial matches.

Confirm the mg/mL figure from your pharmacy label before any draw. If the label only lists the total vial mg and the BAC water volume, divide vial mg by water mL to get concentration. A 30mg vial with 3mL BAC water is 10mg/mL; a 10mg vial with 2mL BAC water is 5mg/mL.

The 30mg Vial Advantage (10mg/mL)

The 30mg vial reconstituted with 3mL of BAC water hits 10mg/mL, and that concentration is the reason it dominates the compounded market. Every titration step from 2.5mg through 10mg lands on a clean round number that fits inside a standard 1mL syringe: 25 IU, 50 IU, 75 IU, 100 IU. The draws sit exactly on quarter, half, three-quarter, and full barrel marks, which makes them easy to read accurately even without magnification.

One 30mg vial covers approximately 12 weekly 2.5mg doses, or roughly two months of starting-dose injections. Once you titrate above 10mg, draws exceed 100 IU and you need a 1.5mL syringe.

When You Need a Larger Syringe

At 5mg/mL, any dose above 5mg exceeds a 1mL syringe. From a 10mg vial the 7.5mg draw is 150 IU (1.5mL); from a 15mg vial the 10mg draw is 200 IU (2mL) and the 15mg draw is 300 IU (3mL). Smaller vials cap out earlier: a 5mg vial cannot deliver any dose above 5mg, and a 10mg vial cannot deliver above 10mg. For users on these smaller vials at 5mg/mL, the practical move is to switch to a 1.5mL syringe at the 7.5mg step (where the vial still has the mg available), or to source the next titration step from a 30mg vial reconstituted at 10mg/mL instead.

At 10mg/mL, the 12.5mg dose is 125 IU and the 15mg dose is 150 IU. Both require a 1.5mL syringe or a split injection (two draws administered close together). Splitting raises the risk of contamination and dosing error, so a 1.5mL syringe is the cleaner choice when available.

Compounded Tirzepatide vs. Brand-Name Pens (Mounjaro / Zepbound)

Brand-name Mounjaro and Zepbound are supplied as pre-filled, pre-dosed autoinjector pens. Each pen contains a single fixed dose (2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, or 15mg) and the user does not draw a volume. The pen delivers the full dose with a button press. Brand-name vials also exist but are single-use and pre-filled to one of the same six fixed doses, so users still do not perform unit math on them.

Compounded tirzepatide ships as a dry powder in a multi-use vial. The user adds BAC water, calculates concentration, and draws the required IU for each dose into a U-100 insulin syringe. This is the only situation in which tirzepatide unit conversion applies. If you are unsure whether you have a pen, a brand vial, or a compounded vial, check the label: brand-name product has the words "Mounjaro" or "Zepbound" and an Eli Lilly NDC; compounded product lists the compounding pharmacy and a mg amount without an Eli Lilly label.

Reverse Lookup: How Many mg Is X Units of Tirzepatide?

The inverse question is just as common: someone reads "draw 40 units" on a clinic instruction and wants to know what mg that translates to. The reverse formula is: mg = (IU / 100) x concentration in mg/mL. The table below covers the most-asked unit values at the two standard concentrations.

Tirzepatide Titration Schedule in Units: Week by Week

The FDA-approved titration for tirzepatide (Mounjaro and Zepbound prescribing information) runs six steps of 4 weeks each, stepping up from 2.5mg to a 15mg maintenance dose. The table below shows the IU draw at each step for both standard concentrations, plus the syringe note. The full schedule hits maximum dose at approximately week 21.

* Exceeds 1mL standard U-100 syringe. Reference schedule only; follow whatever titration your clinic specifies. Some people hold a step longer for tolerability or stop before 15mg once they find an effective dose.

Full 6-step titration at 10mg/mL: clean 1mL fits through 10mg, then 1.5mL syringe territory for 12.5mg and 15mg.

For a deeper protocol view including timing, fasting context, missed-dose handling, and dose-reduction guidance, see the tirzepatide dosing guide. For step-by-step mixing instructions for compounded vials, see the tirzepatide reconstitution guide, or jump straight to the full tirzepatide reconstitution chart for every vial-and-BAC-water combination at a glance.

Video: GLP-1 Dose Confusion - mg vs Units Explained

A physician assistant walks through the conceptual difference between mg and syringe units for GLP-1 medications including tirzepatide. Short, plain-English, and clinically grounded:

References

1. U.S. Food and Drug Administration. ZEPBOUND (tirzepatide) injection - Prescribing Information. Reference ID: 5676099. 2023. accessdata.fda.gov (Zepbound label PDF). (Official FDA prescribing information: confirms the 6-step titration 2.5 to 15mg in 2.5mg increments every 4 weeks, once-weekly subcutaneous administration, 15mg maximum dose for chronic weight management.)
2. U.S. Food and Drug Administration. MOUNJARO (tirzepatide) injection - Prescribing Information. Reference ID: 5023766. 2022. accessdata.fda.gov (Mounjaro label PDF). (Official FDA prescribing information for the T2D indication: confirms same six dose strengths 2.5, 5, 7.5, 10, 12.5, 15mg and identical titration interval as Zepbound.)
3. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022;387(3):205-216. DOI: 10.1056/NEJMoa2206038. (SURMOUNT-1 anchor trial: 20.9% mean body-weight reduction at 15mg over 72 weeks, validating the maximum titration step as a clinically meaningful target.)
4. Eli Lilly and Company. ZEPBOUND Single-Dose Vial Instructions for Use. 2023. pi.lilly.com (Zepbound vial IFU). (Brand-name vial instructions: confirms that Zepbound single-dose vials arrive pre-filled with a fixed mg amount and do not require reconstitution, distinguishing brand vials from compounded powder.)
5. United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding: Sterile Preparations. 2023. usp.org/compounding/general-chapter-797. (Compounding pharmacy standards: governs beyond-use dating, sterility requirements, and stability for reconstituted aqueous compounded preparations like tirzepatide.)
6. BD Diabetes Care. Insulin Syringes - Product Information for U-100 Syringes. bd.com/en-us/products/diabetes/diabetes-products/insulin-syringes. (Manufacturer reference for U-100 insulin syringe calibration: 100 IU equals 1mL, the basis for every IU value on this page.)

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