What's the tirzepatide reconstitution formula?

Dose volume (mL) = target dose (mg) ÷ (vial mg ÷ BAC water mL). On a U-100 insulin syringe, multiply mL × 100 to get units. A 30 mg vial in 1 mL BAC water gives 30 mg/mL; a 2.5 mg starter dose is 0.083 mL = 8.3 units.

How many units are 2.5 mg of tirzepatide?

Depends on the vial concentration. 30 mg/mL = 8.3 units. 15 mg/mL = 16.7 units. 10 mg/mL = 25 units.

How many units are 5 mg of tirzepatide?

30 mg/mL = 16.7 units. 15 mg/mL = 33.3 units. 10 mg/mL = 50 units.

How many units are 7.5 mg of tirzepatide?

30 mg/mL = 25 units. 15 mg/mL = 50 units. 10 mg/mL = 75 units.

How many units are 10 mg of tirzepatide?

30 mg/mL = 33.3 units. 15 mg/mL = 66.7 units. 10 mg/mL = 100 units (max on a U-100 1mL syringe — split into two draws or change concentration).

How many units are 15 mg of tirzepatide?

30 mg/mL = 50 units. 20 mg/mL = 75 units. At 15 mg/mL the draw is 100 units, which fills the entire U-100 1mL syringe — many users prefer 20–30 mg/mL concentrations at this dose.

How much BAC water do I add to a 30 mg tirzepatide vial?

Whatever your pharmacy specified. 1 mL gives 30 mg/mL (good for the full 2.5–15 mg range in one syringe draw); 2 mL gives 15 mg/mL; 3 mL gives 10 mg/mL. Each gives the same total mg in the vial. Higher concentrations mean fewer units per dose; lower concentrations mean more precision at small doses.

Why does tirzepatide concentration vary more than semaglutide?

The FDA-approved tirzepatide dose range is 6× wider than semaglutide's (2.5–15 mg vs 0.25–2.4 mg). A single vial concentration that fits both a 2.5 mg starter draw and a 15 mg max draw is harder to find. Pharmacies typically pick concentration to match the expected maintenance dose, not the starter.

Is compounded tirzepatide the same as Mounjaro or Zepbound?

Same active dual GIP/GLP-1 receptor agonist. The compounded vial is prepared by a 503A pharmacy instead of Eli Lilly. Mounjaro is FDA-approved for type 2 diabetes; Zepbound for chronic weight management. The titration ladder is identical: 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg weekly.

Is compounded tirzepatide still legal in 2026?

Eli Lilly removed Mounjaro and Zepbound from the FDA drug shortage list in late 2024, narrowing the legal window for 503A compounding. As of May 2026, some 503A pharmacies still compound tirzepatide under medical-necessity criteria. 503B bulk compounding is banned. Check with your prescriber and pharmacy on current status before refill.

Why is tirzepatide harder to tolerate than semaglutide?

Tirzepatide is a dual agonist: GLP-1 + GIP receptors. GIP-receptor adaptation takes 2–3 weeks longer than GLP-1 alone. SURMOUNT-1 (NEJM 2022) showed discontinuation rates rose from 1.4% at 2.5 mg to 7% at 5 mg — the 5 mg step is the most common drop-off point.

Calculator · Tirzepatide

Tirzepatide reconstitution calculator: vial mg + BAC water → U-100 units.

Free, no account, runs in your browser. Built for compounded tirzepatide where vial concentration varies 3× more than semaglutide. Worked examples for 30 mg, 60 mg, and 120 mg vials below.

Use the calculator Get Titrate for iOS

Inputs

Three numbers, one answer.

Punch in the vial size, the BAC water you reconstituted with, and your target dose. The math runs live.

Vial sizemg

The total mg in the vial. Common: 5, 10, 15, 30 mg.

BAC water addedmL

The bacteriostatic water volume your pharmacy specified. Usually 1, 2, or 3 mL.

Target dosemg

The mg per injection from your prescription.

Quick presets

Draw this

10.0 units

On a U-100 insulin syringe.

Concentration: 2.50 mg/mL
Dose volume: 0.100 mL
Doses per vial: 20

Formula

dose volume = 0.25 mg ÷ (5 mg ÷ 2 mL)

= 0.25 mg ÷ 2.50 mg/mL

= 0.100 mL = 10.0 units

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The math

One formula. Three numbers.

dose volume (mL) = target dose (mg) ÷ (vial mg ÷ BAC water mL)

On a U-100 insulin syringe, 1 unit equals 0.01 mL. Multiply dose volume in mL by 100 to get units. With tirzepatide specifically, the dose range is 6× wider than semaglutide (2.5–15 mg vs 0.25–2.4 mg). A single vial concentration that fits both your starter and your maintenance dose is the most important pharmacy-side decision — and the one most likely to change on refill.

Mounjaro / Zepbound dose ramp

The FDA-approved tirzepatide schedule.

Every 4 weeks minimum, the dose steps up if tolerated. The tirzepatide ramp is steeper step-for-step than semaglutide — GIP-receptor adaptation takes 2–3 weeks longer than GLP-1 alone.

Week	Dose	Notes
Weeks 1–4	2.5 mg	Starter. Sub-therapeutic; GIP/GLP-1 receptor adaptation step.
Weeks 5–8	5 mg	First therapeutic step. Discontinuation rises from 1.4% → 7% per SURMOUNT-1.
Weeks 9–12	7.5 mg	Common long-term maintenance for moderate weight loss goals.
Weeks 13–16	10 mg	Common long-term maintenance for more aggressive goals.
Weeks 17–20	12.5 mg	Plateau-breaking step. Hold 4 weeks minimum.
Week 21+	15 mg	Max dose. SURMOUNT-1 mean weight loss: 22.5% at 72 weeks.

Source: Mounjaro and Zepbound FDA labels; SURMOUNT-1 NEJM 2022. Full schedule: tirzepatide dose schedule guide.

Worked examples

Common tirzepatide vial concentrations, in units.

Compounded tirzepatide vials are typically 30 mg, 60 mg, or 120 mg. The reconstitution volume determines whether your max dose fits in a single U-100 syringe draw.

Vial + BAC water	Concentration	Target dose	Dose volume	U-100 units
30 mg / 1 mL BAC	30.00 mg/mL	2.5 mg	0.083 mL	8.3 units
30 mg / 1 mL BAC	30.00 mg/mL	5 mg	0.167 mL	16.7 units
30 mg / 1 mL BAC	30.00 mg/mL	10 mg	0.333 mL	33.3 units
30 mg / 2 mL BAC	15.00 mg/mL	5 mg	0.333 mL	33.3 units
30 mg / 2 mL BAC	15.00 mg/mL	10 mg	0.667 mL	66.7 units
30 mg / 3 mL BAC	10.00 mg/mL	5 mg	0.500 mL	50 units
60 mg / 2 mL BAC	30.00 mg/mL	10 mg	0.333 mL	33.3 units
60 mg / 3 mL BAC	20.00 mg/mL	15 mg	0.750 mL	75 units
120 mg / 4 mL BAC	30.00 mg/mL	12.5 mg	0.417 mL	41.7 units

Compounded tirzepatide context

Same molecule, six-fold dose range, one vial concentration.

Compounded tirzepatide is the same dual GIP/GLP-1 receptor agonist as Mounjaro and Zepbound, prepared by a 503A pharmacy instead of Eli Lilly. The molecule is identical. The active mass per dose is identical. What differs is the vial concentration and the regulatory state.

Eli Lilly removed Mounjaro and Zepbound from the FDA drug shortage list in late 2024, narrowing the legal window for 503A compounding. As of May 2026, some 503A pharmacies still compound under medical-necessity criteria. 503B bulk compounding is banned. Confirm legal status with your prescriber and pharmacy before each refill.

Tirzepatide's 6× dose range (2.5–15 mg) creates a pharmacy-side trade-off that semaglutide's 10× tighter range (0.25–2.4 mg) doesn't: pick a concentration high enough that 15 mg fits a single syringe draw, low enough that 2.5 mg isn't a microliter draw. Most pharmacies target 15–30 mg/mL. If yours doesn't, the calculator above will catch the mismatch before you draw the wrong volume.

Discontinuation rose from ~1.4% at 2.5 mg to ~7% at 5 mg in SURMOUNT-1 (NEJM 2022) — the 5 mg step is the most common drop-off point. Holding 5 mg for an extra 4 weeks before advancing to 7.5 mg is a defensible move; the FDA label specifies minimum, not maximum, hold times.

Full guide: Compounded tirzepatide — regulatory state, concentrations, what to verify.

Common questions

Tirzepatide reconstitution, answered.

What's the tirzepatide reconstitution formula?: Dose volume (mL) = target dose (mg) ÷ (vial mg ÷ BAC water mL). On a U-100 insulin syringe, multiply mL × 100 to get units. A 30 mg vial in 1 mL BAC water gives 30 mg/mL; a 2.5 mg starter dose is 0.083 mL = 8.3 units.
How many units are 2.5 mg of tirzepatide?: Depends on the vial concentration. 30 mg/mL = 8.3 units. 15 mg/mL = 16.7 units. 10 mg/mL = 25 units.
How many units are 5 mg of tirzepatide?: 30 mg/mL = 16.7 units. 15 mg/mL = 33.3 units. 10 mg/mL = 50 units.
How many units are 7.5 mg of tirzepatide?: 30 mg/mL = 25 units. 15 mg/mL = 50 units. 10 mg/mL = 75 units.
How many units are 10 mg of tirzepatide?: 30 mg/mL = 33.3 units. 15 mg/mL = 66.7 units. 10 mg/mL = 100 units (max on a U-100 1mL syringe — split into two draws or change concentration).
How many units are 15 mg of tirzepatide?: 30 mg/mL = 50 units. 20 mg/mL = 75 units. At 15 mg/mL the draw is 100 units, which fills the entire U-100 1mL syringe — many users prefer 20–30 mg/mL concentrations at this dose.
How much BAC water do I add to a 30 mg tirzepatide vial?: Whatever your pharmacy specified. 1 mL gives 30 mg/mL (good for the full 2.5–15 mg range in one syringe draw); 2 mL gives 15 mg/mL; 3 mL gives 10 mg/mL. Each gives the same total mg in the vial. Higher concentrations mean fewer units per dose; lower concentrations mean more precision at small doses.
Why does tirzepatide concentration vary more than semaglutide?: The FDA-approved tirzepatide dose range is 6× wider than semaglutide's (2.5–15 mg vs 0.25–2.4 mg). A single vial concentration that fits both a 2.5 mg starter draw and a 15 mg max draw is harder to find. Pharmacies typically pick concentration to match the expected maintenance dose, not the starter.
Is compounded tirzepatide the same as Mounjaro or Zepbound?: Same active dual GIP/GLP-1 receptor agonist. The compounded vial is prepared by a 503A pharmacy instead of Eli Lilly. Mounjaro is FDA-approved for type 2 diabetes; Zepbound for chronic weight management. The titration ladder is identical: 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg weekly.
Is compounded tirzepatide still legal in 2026?: Eli Lilly removed Mounjaro and Zepbound from the FDA drug shortage list in late 2024, narrowing the legal window for 503A compounding. As of May 2026, some 503A pharmacies still compound tirzepatide under medical-necessity criteria. 503B bulk compounding is banned. Check with your prescriber and pharmacy on current status before refill.
Why is tirzepatide harder to tolerate than semaglutide?: Tirzepatide is a dual agonist: GLP-1 + GIP receptors. GIP-receptor adaptation takes 2–3 weeks longer than GLP-1 alone. SURMOUNT-1 (NEJM 2022) showed discontinuation rates rose from 1.4% at 2.5 mg to 7% at 5 mg — the 5 mg step is the most common drop-off point.

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