Tirzepatide reconstitution calculator
How many units of a reconstituted tirzepatide vial make up the dose you want — and how much bacteriostatic water to add to land on a round number. Same code as the TherapyLog app, no account needed.
Tirzepatide is dosed in whole milligrams — 2.5 up to 15 mg a week — which makes its reconstitution arithmetic different in character from semaglutide's. The doses are ten to sixty times larger, so a vial that would hold twenty semaglutide doses holds four tirzepatide ones, and the volume you draw is large enough that a 0.3 ml syringe runs out of barrel before the dose runs out of milligrams.
That is the practical trap, and it is a ceiling rather than an inconvenience. Take a 10 mg vial reconstituted in 1 ml of bacteriostatic water — 10 mg per millilitre, the most concentrated a 10 mg vial usefully gets. A 2.5 mg dose is 25 units and a 10 mg dose fills the barrel exactly; 12.5 mg and 15 mg do not fit at all. Adding more water makes it worse, not better: the same vial in 2 ml puts a 15 mg dose at three millilitres, three full syringes. The milligrams in the vial set the largest dose you can draw in one go, and no amount of water changes that — only a larger or more concentrated vial does.
Tirzepatide milligrams to insulin units
Computed for a 10 mg vial reconstituted in 1 ml of bacteriostatic water, which gives 10 mg per ml (10,000 mcg/ml), read off a U-100 syringe. The steps are the approved titration steps (2.5, 5, 7.5, 10, 12.5, 15 mg weekly) — they are what the numbers are indexed to, not advice about which one applies to anyone. Change the vial or the water above and every figure moves; the calculator is the authority, this table is the common case.
| Tirzepatide dose | Volume to draw | On a U-100 syringe |
|---|---|---|
| 2.5 mg | 0.25 ml | 25 units |
| 5 mg | 0.5 ml | 50 units |
| 7.5 mg | 0.75 ml | 75 units |
| 10 mg | 1 ml | 100 units |
| 12.5 mg | 1.25 ml | 125 units (more than one syringe) |
| 15 mg | 1.5 ml | 150 units (more than one syringe) |
Why tirzepatide is reconstituted the way it is
Tirzepatide is a dual GIP and GLP-1 receptor agonist, and like semaglutide it ships as a dry powder for stability. Its modelled half-life is about five days, so weekly dosing still accumulates — levels plateau after roughly three to four weeks rather than five.
The approved titration is deliberately slow for tolerability rather than for pharmacokinetics, which is why the steps are four weeks apart even though the drug reaches steady state sooner than that.
What the app knows about Tirzepatide
Generated from the same entry the app's encyclopedia reads, so this page and the app cannot disagree about it.
- Also known as
- Mounjaro, Zepbound
- Class
- GLP-1 / Metabolic
- Modelled half-life
- 5 days
- Time to peak
- 24 h
- Formulation
- Aqueous (reconstituted powder)
- Regulatory status
- FDA APPROVED for T2 diabetes (Mounjaro) and obesity (Zepbound). Off-label for general weight loss.
- Monitoring panel
- Same as Semaglutide. HbA1c, fasting glucose, lipids, weight monthly.
- Before mixing
- Sealed powder tolerates room temperature in transit, but keep it refrigerated at 2–8 °C (36–46 °F) for anything beyond a few weeks, or frozen for months. Keep it dark — the carton it shipped in is doing a job.
- After mixing
- Once reconstituted with bacteriostatic water: refrigerate at 2–8 °C and use within about 28 days. The benzyl alcohol in bacteriostatic water is what buys that window — plain sterile water has no preservative, so a vial mixed with it should be treated as one sitting only. Kits are usually ten vials: only the one you mixed is on that 28-day clock — the sealed ones keep their own, much longer shelf life, so store them as powder, not as solution.
- What ruins it
- Do not freeze a reconstituted vial. Repeated freeze–thaw is one of the more reliable ways to degrade a peptide.
- Handling caveat
- General handling practice for this formulation. Your supplier’s own insert or COA overrides anything here.
Dosing rows from that entry
Established clinical use These are the schedules the entry records, reproduced so you can see what the milligram figures above are indexed to. Which one applies to a particular person is a prescribing decision, and this page does not make it.
| Label | Amount | Route and frequency |
|---|---|---|
| Starting | 2.5mg/week | Weekly SubQ |
| Maintenance | 5-10mg/week | Weekly SubQ |
| Maximum | 15mg/week | Weekly SubQ |
How the math works
volume to draw = dose (mcg) ÷ 10,000 mcg/ml
units (U-100) = volume to draw (ml) × 100
The rules built into the calculator: a practical draw lands on a half-unit and is at least two units; U-100 means a hundred units per millilitre, so 0.1 ml is 10 units on any U-100 syringe regardless of its barrel size; and a draw that exceeds the barrel is flagged rather than silently split across injections.
Questions people ask about tirzepatide reconstitution
How many units is 2.5 mg of tirzepatide?
At 10 mg in 1 ml — 10,000 mcg/ml — it is 25 units on a U-100 syringe. At any other reconstitution it is a different number, which is why the table above states the vial and the diluent volume it was computed for.
What size vial should I reconstitute?
Whichever one you have — the calculator takes the strength as an input. What the vial size decides is how many doses it holds, and therefore whether it will still be good when you reach the last one: a 10 mg vial cannot supply the largest step above at all — 15 mg is more than the whole vial holds, so that dose needs a bigger or a more concentrated vial, not more water, and about 4 of the smallest. A vial holding more doses than its post-mixing window allows is a vial you will be throwing part of away, which is an argument for mixing a smaller working volume rather than a bigger one.
Does tirzepatide accumulate between doses?
Its modelled half-life is 5 days. A rough guide is that levels keep building for about five half-lives before they plateau, so the effect of a dose you take today is partly the effect of the doses before it. The Tirzepatide half-life page shows the curve and the steady-state arithmetic.
How long does it keep once mixed?
The entry's handling rule is in the fact box above, along with the caveat that comes with it: your supplier's own insert or certificate of analysis overrides anything generic. As a rule the constraint is the diluent rather than the peptide — bacteriostatic water's preservative is what makes repeated entry reasonable, and it is the reason a mixed vial is a weeks-not-months proposition.
Related: Tirzepatide half-life and steady state, the generic reconstitution calculator, and the insulin syringe unit converter.
The app stores this vial's strength, its concentration and the date you mixed it, and counts the doses down as you log them.
Save this dose to your logThis calculator does the arithmetic you typed and nothing else. It does not know what is actually in your vial, whether the label is accurate, or anything about you. Confirm the vial strength and the diluent volume on your own label before you draw, and take dosing decisions to a qualified provider.