Tirzepatide
How to reconstitute the 20 mg vial and convert any target dose into insulin units. Tirzepatide is the prescription drug Mounjaro/Zepbound, dosed once weekly per its FDA label (2.5 mg start, max 15 mg). The approved product is a metered pen with no reconstitution; the math here is for research vials only.
Calculate for your vial
Enter the mg on your Tirzepatide vial, the bacteriostatic water you added, and your target dose — it works out the exact units to draw on a U-100 insulin syringe, for whatever you personally have.
Reconstitution Calculator
Check the decimal. A misplaced decimal point here is a 10× dosing error. Re-read every number, and confirm your dose with a licensed clinician before you draw.
Educational only — not a dosing recommendation. This tool does the measurement math; it does not tell you what to take. On a U-100 insulin syringe, 100 units = 1 mL.
Dosing schedule
Tirzepatide · fixed weekly step-up schedule
A fixed weekly titration ladder. Heavier individuals more often titrate toward the 10–15 mg maintenance doses (the largest weight loss), while lighter responders can hold at 5 mg.
- 12.5 mg/wkWeeks 1–4Starting dose (initiation only)
- 25 mg/wkWeeks 5–8Maintenance dose
- 37.5 mg/wkWeeks 9–12Step-up
- 410 mg/wkWeeks 13–16Maintenance dose
- 512.5 mg/wkWeeks 17–20Step-up
- 615 mg/wkWeek 21+Maintenance / max
Everyone starts at 2.5 mg and increases in 2.5 mg steps no sooner than every 4 weeks — the approved maintenance doses are 5, 10, or 15 mg (7.5 and 12.5 are step-ups, not endpoints). Heavier people more commonly titrate toward 10–15 mg; lighter responders can hold at 5 mg. The dose is chosen by tolerability and response under medical supervision, not from a weight calculation.
Source: FDA label — Zepbound® (tirzepatide). Educational only — not medical advice and not a dosing recommendation. Any dosing decision belongs with a licensed clinician.
1 · Find your dose
Pick what you're using Tirzepatide for and how much bacteriostatic water you added — this pulls out the exact units to draw and how often people report using it.
to draw 2.5 mg–15 mg at 1 mL water
20 mg/mL · 200 mcg per unit
- How often
- Once weekly (subcutaneous)
- Cycle
- Increase by 2.5 mg every ≥4 weeks to the target dose, per label
2 · Reconstitute it cleanly, step by step
How to turn the 20 mg powder into a measured liquid with clean, sterile technique. More water means each insulin unit holds less peptide — easier to measure small amounts accurately.
1Swab the stoppers
Wipe the rubber top of each vial with an alcohol pad and let it air-dry.
2Draw the water
Pull your bacteriostatic water up into the insulin syringe.
3Reconstitute
Inject it slowly down the inside wall of the peptide vial — never straight onto the powder.
4Swirl to dissolve
Gently swirl until the powder fully dissolves into a clear liquid. Never shake.
5Equalize, then draw
To draw a dose: push in an equal amount of air first to equalize the pressure, then pull your dose.
- 1
Swab both tops
Wipe the rubber top of the bacteriostatic-water vial and the Tirzepatide vial stopper with a fresh alcohol pad, and let them air-dry. Never touch the needle or the stoppers after wiping.
Alcohol swab · let dry - 2
Draw the water
First pull 1 mL of air into the syringe and inject it into the bacteriostatic-water vial to equalize the pressure, then draw your 1 mL of water back out. Inject it into the Tirzepatide vial down the inside glass wall, not onto the powder.
1 mL BAC water - 3
Swirl, don't shake
Gently swirl the 20 mg vial until the powder fully dissolves into a clear liquid. Never shake — shaking can damage the peptide and foam the solution.
Swirl, don't shake - 4
Know your strength
The vial is now 20 mg/mL. Each unit on a U-100 syringe holds about 200 mcg.
20 mg/mL - 5
Re-swab & draw your dose
Wipe the stopper again. With a fresh insulin syringe, pull back 25 units of air and inject it into the vial to equalize the pressure, then draw 25 units (0.25 mL) for a 5 mg dose.
25 units - 6
Store it right
Keep the mixed vial in the fridge, away from light. Use a new sterile syringe every time, never share, and drop used sharps in a proper container.
Refrigerate · fresh needle
What each water volume gives you:
3 · Full units reference
Every bacteriostatic-water volume (rows) against every target dose (columns) — each cell is the U-100 units and the exact draw in mL. The highlighted row is the easiest volume to measure.
| BAC water | Concentration | Per unit | 2.5 mg | 5 mg | 7.5 mg |
|---|---|---|---|---|---|
| 1 mLeasy pick | 20 mg/mL | 200 mcg | 12.5u0.125 mL | 25u0.25 mL | 37.5u0.375 mL |
| 2 mL | 10 mg/mL | 100 mcg | 25u0.25 mL | 50u0.5 mL | 75u0.75 mL |
| 3 mL | 6.67 mg/mL | 66.67 mcg | 37.5u0.375 mL | 75u0.75 mL | 112.5u1.125 mL |
4 · Everyday usage
Tirzepatide is the FDA-approved prescription drug Mounjaro/Zepbound, supplied as a finished metered pen or single-dose vial — there is no patient reconstitution step for the approved product. The figures below are the approved-drug label titration schedule for reference only, not a recommendation to reconstitute a research vial.
Approved-drug label titration (Zepbound/Mounjaro, SC)
Label-citedThe approved product starts at 2.5 mg once weekly and is stepped up by 2.5 mg every 4 weeks as tolerated, injected under the skin.
- Reported amount
- 2.5 mg–15 mg≈ 12.5–75 units @ 1 mL
- Frequency
- Once weekly (subcutaneous)
- Cycle
- Increase by 2.5 mg every ≥4 weeks to the target dose, per label
FDA prescribing information for Mounjaro/Zepbound (tirzepatide): 2.5 mg once weekly for 4 weeks, then increased in 2.5 mg steps every ≥4 weeks; maximum 15 mg once weekly. Prescription-only, delivered by a metered pen or single-dose vial — not a recommendation to dose a research vial.
Frequently asked questions
How many insulin units is 2.5 mg of Tirzepatide from a 20 mg vial?
- Reconstituting a 20 mg vial with 1 mL of bacteriostatic water gives 20 mg/mL — about 200 mcg per unit. Drawing 2.5 mg is 0.125 mL, or 12.5 units on a U-100 insulin syringe. This is measurement math, not a dose recommendation.
How many insulin units is 5 mg of Tirzepatide from a 20 mg vial?
- Reconstituting a 20 mg vial with 1 mL of bacteriostatic water gives 20 mg/mL — about 200 mcg per unit. Drawing 5 mg is 0.25 mL, or 25 units on a U-100 insulin syringe. This is measurement math, not a dose recommendation.
Is the approved tirzepatide product reconstituted by the patient?
- No. Mounjaro and Zepbound are finished, FDA-regulated products supplied as metered pens or pre-filled single-dose vials, with no mixing step. The reconstitution math here applies only to lyophilized research vials, which are not the approved medicine. Tirzepatide is prescription-only; dosing belongs with a licensed clinician.
WikiPeps is a community reference. Reconstitution figures are deterministic measurement math; usage figures are sourced and labeled. Nothing here is medical advice, a recommendation, or an offer to sell peptides — dosing decisions belong with a licensed clinician.