How many units is 2.5 mg of tirzepatide?

It depends entirely on the concentration, which is why there is no single answer. At 5 mg/mL, 2.5 mg is 50 units. At 10 mg/mL it is 25 units, at 15 mg/mL it is 16.75 units, at 20 mg/mL it is 12.5 units and at 30 mg/mL it is only 8.25 units. Read the concentration off your vial label or work it out from the vial strength and the water added before you draw anything.

How do I convert tirzepatide mg to units?

Multiply the dose in mg by 100 and divide by the concentration in mg/mL. The 100 comes from the definition of a U-100 syringe: 100 units is 1 mL. So 5 mg at 20 mg/mL is 5 × 100 ÷ 20 = 25 units. To go the other way, multiply the units by the concentration and divide by 100: 25 units at 20 mg/mL is 5 mg.

What is the tirzepatide dosage schedule?

Both FDA-approved products start at 2.5 mg injected subcutaneously once weekly and increase in 2.5 mg increments after at least 4 weeks on the current dose, giving the ladder 2.5, 5, 7.5, 10, 12.5 and 15 mg. The maximum in adults is 15 mg once weekly for both. Compounded tirzepatide is not FDA-approved and its schedule is set by the prescriber, not by a label.

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

Whatever your prescriber or compounding pharmacy specified — the volume is part of the prescription, not a free choice, because it sets the concentration every subsequent dose is measured against. For reference, 30 mg with 1 mL of water gives 30 mg/mL and a 2.5 mg dose becomes 8.25 units; the same vial with 2 mL gives 15 mg/mL and the same dose becomes 16.75 units. Never guess the volume and never reconstitute to a concentration nobody told you to use.

Why will my 15 mg tirzepatide dose not fit in the syringe?

Because the vial is too dilute for the dose. 15 mg out of a 10 mg/mL vial is 1.5 mL, which is 150 units — one and a half 1 mL barrels. You need at least 15 mg/mL for 15 mg to come in at 100 units, and at 30 mg/mL it is only 50 units. A draw over 100 units means the concentration or the dose is wrong; check with your prescriber rather than splitting the injection.

How many units is a Zepbound or Mounjaro vial on an insulin syringe?

Always the same number, whatever the strength, because the volume is fixed. Every single-dose pen and single-dose vial holds 0.5 mL, which is 50 units on a U-100 scale, from the 2.5 mg presentation to the 15 mg one. Every injection from a multi-dose vial or KwikPen is 0.6 mL, which is 60 units. Both labels nonetheless tell you to use a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose, not an insulin syringe.

Is 2.5 mg the same as 2,500 mcg of tirzepatide?

Yes. There are 1,000 micrograms in a milligram, so 2.5 mg is 2,500 mcg, 7.5 mg is 7,500 mcg and 15 mg is 15,000 mcg. Compounded prescriptions are written both ways, which is itself a source of confusion — convert to one unit and stay in it for the whole calculation.

Why do two people on the same tirzepatide dose draw different numbers of units?

Because they have different concentrations in the vial. A man with a 30 mg vial in 1 mL of water draws 5 mg as 16.75 units; a man with a 10 mg vial in 2 mL of water draws the identical 5 mg as 100 units. Six times the marks, the same drug. Never copy a unit count from a forum, a friend or a previous vial — recalculate from your own concentration every time the vial changes.

Free dosing tool

Tirzepatide units converter

Convert a prescribed tirzepatide dose between milligrams, micrograms and insulin syringe units at your own reconstituted concentration — with the full chart below.

Reviewed by: Alpha Health Finder Editorial Team
Last reviewed: September 2026

Why “units” means nothing without the concentration

A U-100 insulin syringe is graduated so that 100 units is one millilitre. It measures volume, not drug. The syringe has no idea what is in it, so the same 25-unit mark delivers 1.25 mg from a vial reconstituted to 5 mg/mL and 7.5 mg from one reconstituted to 30 mg/mL — a six-fold difference off an identical-looking draw.

Branded tirzepatide sidesteps this entirely. Both FDA-approved products — MOUNJARO for type 2 diabetes and ZEPBOUND for weight management and obstructive sleep apnoea — ship as a ready-made solution at a fixed strength, and the volume is fixed too: every single-dose pen and single-dose vial holds 0.5 mL whatever its strength, and every injection from a multi-dose vial or KwikPen is 0.6 mL. That is why a 2.5 mg vial and a 15 mg vial look identical on a syringe: both are 50 units. The strength changes, the volume does not.

Compounded tirzepatide does not work that way. It arrives as a lyophilised powder — commonly 10 mg, 20 mg, 30 mg, 40 mg, 60 mg in the vial — and the concentration is created at the point the bacteriostatic water is added. Divide the vial strength by the volume of water and you have your mg/mL. Nothing else about the product tells you.

The FDA has warned specifically about this class of error. Its alert on unapproved GLP-1 drugs used for weight loss describes dosing errors resulting from patients measuring and self-administering incorrect doses, and from health care professionals miscalculating doses, with adverse events some of which required hospitalisation. The converter below exists to make one specific arithmetic mistake harder to make.

The formula

concentration (mg/mL) = vial strength (mg) ÷ bacteriostatic water (mL)

volume (mL) = dose (mg) ÷ concentration (mg/mL)

units (U-100) = volume (mL) × 100

units = dose (mg) × 100 ÷ concentration (mg/mL)

dose (mg) = units × concentration (mg/mL) ÷ 100

The 100 is not a fudge factor — it is the definition of U-100: the barrel is graduated so 100 units is exactly 1 mL. Doses written in micrograms convert first: 2,500 mcg is 2.5 mg. Because tirzepatide doses reach 15 mg, check the volume as well as the unit count — anything over 100 units will not fit in one 1 mL barrel.

Worked example

A 40 mg vial of compounded tirzepatide reconstituted with 2 mL of bacteriostatic water, prescribed dose 5 mg:

Concentration = 40 mg ÷ 2 mL = 20 mg/mL
Volume = 5 mg ÷ 20 mg/mL = 0.25 mL
Units = 0.25 mL × 100 = 25 units on a U-100 syringe
Each single unit mark delivers 0.2 mg (200 mcg)
At 5 mg the 40 mg vial holds 8 whole doses

Tirzepatide mg to units chart

Units on a U-100 insulin syringe for each dose, at each reconstituted concentration. Find your concentration across the top, your prescribed dose down the side.

Dose	5 mg/mL10 mg + 2 mL	10 mg/mL10 mg + 1 mL	15 mg/mL30 mg + 2 mL	20 mg/mL20 mg + 1 mL	30 mg/mL30 mg + 1 mL
1.25 mg1250 mcg	25 u0.25 mL	12.5 u0.125 mL	8.25 u0.083 mL	6.25 u0.063 mL	4.25 u0.042 mL
2.5 mg2500 mcg	50 u0.5 mL	25 u0.25 mL	16.75 u0.167 mL	12.5 u0.125 mL	8.25 u0.083 mL
3.75 mg3750 mcg	75 u0.75 mL	37.5 u0.375 mL	25 u0.25 mL	18.75 u0.188 mL	12.5 u0.125 mL
5 mg5000 mcg	100 u1 mL	50 u0.5 mL	33.25 u0.333 mL	25 u0.25 mL	16.75 u0.167 mL
7.5 mg7500 mcg	150 u1.5 mL — over one syringe	75 u0.75 mL	50 u0.5 mL	37.5 u0.375 mL	25 u0.25 mL
10 mg10000 mcg	200 u2 mL — over one syringe	100 u1 mL	66.75 u0.667 mL	50 u0.5 mL	33.25 u0.333 mL
12.5 mg12500 mcg	250 u2.5 mL — over one syringe	125 u1.25 mL — over one syringe	83.25 u0.833 mL	62.5 u0.625 mL	41.75 u0.417 mL
15 mg15000 mcg	300 u3 mL — over one syringe	150 u1.5 mL — over one syringe	100 u1 mL	75 u0.75 mL	50 u0.5 mL

Rounded to the quarter-unit mark — the finest split anyone can judge between two printed lines, rather than a graduation any barrel actually carries. A draw above 100 units does not fit in a single 1 mL syringe — that is a signal the vial is too dilute for the dose, not an instruction to inject twice. At the 15 mg label maximum you need at least 15 mg/mL for the dose to fit in one barrel.

Tirzepatide reconstitution chart — vial strength × bacteriostatic water

The concentration each combination produces, and what the 2.5 mg starting dose becomes on the syringe at that concentration.

Vial	1 mL water	2 mL water	3 mL water	5 mL water
10 mg10000 mcg powder	10 mg/mL2.5 mg = 25 u	5 mg/mL2.5 mg = 50 u	3.333 mg/mL2.5 mg = 75 u	2 mg/mL2.5 mg = 125 u — over one syringe
20 mg20000 mcg powder	20 mg/mL2.5 mg = 12.5 u	10 mg/mL2.5 mg = 25 u	6.667 mg/mL2.5 mg = 37.5 u	4 mg/mL2.5 mg = 62.5 u
30 mg30000 mcg powder	30 mg/mL2.5 mg = 8.25 u	15 mg/mL2.5 mg = 16.75 u	10 mg/mL2.5 mg = 25 u	6 mg/mL2.5 mg = 41.75 u
40 mg40000 mcg powder	40 mg/mL2.5 mg = 6.25 u	20 mg/mL2.5 mg = 12.5 u	13.333 mg/mL2.5 mg = 18.75 u	8 mg/mL2.5 mg = 31.25 u
60 mg60000 mcg powder	60 mg/mL2.5 mg = 4.25 u	30 mg/mL2.5 mg = 8.25 u	20 mg/mL2.5 mg = 12.5 u	12 mg/mL2.5 mg = 20.75 u

Compounded tirzepatide has no FDA-approved labelling, so these vial strengths are the ones commonly supplied rather than an authoritative list — read your own vial and use the water volume your pharmacy specified. The powder adds negligible volume, so the reconstituted volume is taken as the water added. At the strongest concentrations the quarter-unit resolution of the syringe starts to matter: 2.5 mg at 60 mg/mL is 4.17 units, which can only be drawn as 4.25. A more dilute vial measures a small dose more accurately; too dilute and a 15 mg dose no longer fits in the barrel.

Label dose escalation in syringe units

The FDA-approved tirzepatide escalation ladder — identical for Mounjaro and Zepbound — converted to U-100 units at four common compounded concentrations.

Stage	10 mg/mL	15 mg/mL	20 mg/mL	30 mg/mL
Weeks 1–42.5 mg · 2500 mcg	25 u0.25 mL	16.75 u0.167 mL	12.5 u0.125 mL	8.25 u0.083 mL
Weeks 5–85 mg · 5000 mcg	50 u0.5 mL	33.25 u0.333 mL	25 u0.25 mL	16.75 u0.167 mL
Weeks 9–127.5 mg · 7500 mcg	75 u0.75 mL	50 u0.5 mL	37.5 u0.375 mL	25 u0.25 mL
Weeks 13–1610 mg · 10000 mcg	100 u1 mL	66.75 u0.667 mL	50 u0.5 mL	33.25 u0.333 mL
Weeks 17–2012.5 mg · 12500 mcg	125 u1.25 mL — over one syringe	83.25 u0.833 mL	62.5 u0.625 mL	41.75 u0.417 mL
Week 21 onward15 mg · 15000 mcg	150 u1.5 mL — over one syringe	100 u1 mL	75 u0.75 mL	50 u0.5 mL

Both labels start at 2.5 mg once weekly and increase in 2.5 mg increments after at least 4 weeks on the current dose, to a maximum of 15 mg once weekly in adults. The week numbers above are the EARLIEST a dose can be reached if every step is taken at exactly four weeks; "at least 4 weeks" has no upper bound and neither label requires anyone to keep climbing. Mounjaro escalates only if additional glycaemic control is needed and caps paediatric patients aged 10 and over at 10 mg. Zepbound's recommended maintenance dosages are 5 mg, 10 mg, 15 mg for weight reduction and 10 mg or 15 mg for obstructive sleep apnoea — 2.5 mg is for initiation only and is not approved as a maintenance dosage. Your prescription governs; this is a reference, not a plan.

Mounjaro and Zepbound presentations — strength, volume and syringe units

What the approved products actually contain. The strength changes down the column; the injection volume does not, which is why the unit count never moves.

Dose per injection	Single-dose pen or vial0.5 mL fill	Multi-dose vial or KwikPen4 × 0.6 mL
2.5 mg2500 mcg once weekly	5 mg/mL2.5 mg/0.5 mL · 50 u	4.17 mg/mL10 mg/2.4 mL · 60 u
5 mg5000 mcg once weekly	10 mg/mL5 mg/0.5 mL · 50 u	8.33 mg/mL20 mg/2.4 mL · 60 u
7.5 mg7500 mcg once weekly	15 mg/mL7.5 mg/0.5 mL · 50 u	12.5 mg/mL30 mg/2.4 mL · 60 u
10 mg10000 mcg once weekly	20 mg/mL10 mg/0.5 mL · 50 u	16.67 mg/mL40 mg/2.4 mL · 60 u
12.5 mg12500 mcg once weekly	25 mg/mL12.5 mg/0.5 mL · 50 u	20.83 mg/mL50 mg/2.4 mL · 60 u
15 mg15000 mcg once weekly	30 mg/mL15 mg/0.5 mL · 50 u	25 mg/mL60 mg/2.4 mL · 60 u

Section 3 of both the Mounjaro and Zepbound labels lists the same six strengths in the same presentations. The pens dose themselves, so the unit figures matter only for the single-dose and multi-dose vials — and for those the labels tell you to use "a syringe appropriate for dose administration (e.g., a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose)", not an insulin syringe you have converted by eye. The mg/mL figures are computed from the strength and fill volume, so 4.17 and 16.7 appear here as the exact 4.17 and 16.67 the label rounds.

Frequently asked questions

How many units is 2.5 mg of tirzepatide?: It depends entirely on the concentration, which is why there is no single answer. At 5 mg/mL, 2.5 mg is 50 units. At 10 mg/mL it is 25 units, at 15 mg/mL it is 16.75 units, at 20 mg/mL it is 12.5 units and at 30 mg/mL it is only 8.25 units. Read the concentration off your vial label or work it out from the vial strength and the water added before you draw anything.
How do I convert tirzepatide mg to units?: Multiply the dose in mg by 100 and divide by the concentration in mg/mL. The 100 comes from the definition of a U-100 syringe: 100 units is 1 mL. So 5 mg at 20 mg/mL is 5 × 100 ÷ 20 = 25 units. To go the other way, multiply the units by the concentration and divide by 100: 25 units at 20 mg/mL is 5 mg.
What is the tirzepatide dosage schedule?: Both FDA-approved products start at 2.5 mg injected subcutaneously once weekly and increase in 2.5 mg increments after at least 4 weeks on the current dose, giving the ladder 2.5, 5, 7.5, 10, 12.5 and 15 mg. The maximum in adults is 15 mg once weekly for both. Compounded tirzepatide is not FDA-approved and its schedule is set by the prescriber, not by a label.
Do Mounjaro and Zepbound use the same tirzepatide doses?: The same six strengths and the same 2.5 mg starting dose, but not the same dosage sections. Zepbound names a recommended maintenance dosage — 5 mg, 10 mg, 15 mg once weekly for weight reduction, or 10 mg or 15 mg for obstructive sleep apnoea — and states that 2.5 mg is for initiation only and is not approved as a maintenance dosage. Mounjaro names no maintenance dosage at all and escalates only if additional glycaemic control is needed, so any rung can be a destination. Mounjaro also caps paediatric patients aged 10 and over at 10 mg; Zepbound has no paediatric dosage.
How much bacteriostatic water do I add to a 30 mg tirzepatide vial?: Whatever your prescriber or compounding pharmacy specified — the volume is part of the prescription, not a free choice, because it sets the concentration every subsequent dose is measured against. For reference, 30 mg with 1 mL of water gives 30 mg/mL and a 2.5 mg dose becomes 8.25 units; the same vial with 2 mL gives 15 mg/mL and the same dose becomes 16.75 units. Never guess the volume and never reconstitute to a concentration nobody told you to use.
Why will my 15 mg tirzepatide dose not fit in the syringe?: Because the vial is too dilute for the dose. 15 mg out of a 10 mg/mL vial is 1.5 mL, which is 150 units — one and a half 1 mL barrels. You need at least 15 mg/mL for 15 mg to come in at 100 units, and at 30 mg/mL it is only 50 units. A draw over 100 units means the concentration or the dose is wrong; check with your prescriber rather than splitting the injection.
How many units is a Zepbound or Mounjaro vial on an insulin syringe?: Always the same number, whatever the strength, because the volume is fixed. Every single-dose pen and single-dose vial holds 0.5 mL, which is 50 units on a U-100 scale, from the 2.5 mg presentation to the 15 mg one. Every injection from a multi-dose vial or KwikPen is 0.6 mL, which is 60 units. Both labels nonetheless tell you to use a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose, not an insulin syringe.
Is 2.5 mg the same as 2,500 mcg of tirzepatide?: Yes. There are 1,000 micrograms in a milligram, so 2.5 mg is 2,500 mcg, 7.5 mg is 7,500 mcg and 15 mg is 15,000 mcg. Compounded prescriptions are written both ways, which is itself a source of confusion — convert to one unit and stay in it for the whole calculation.
Why do two people on the same tirzepatide dose draw different numbers of units?: Because they have different concentrations in the vial. A man with a 30 mg vial in 1 mL of water draws 5 mg as 16.75 units; a man with a 10 mg vial in 2 mL of water draws the identical 5 mg as 100 units. Six times the marks, the same drug. Never copy a unit count from a forum, a friend or a previous vial — recalculate from your own concentration every time the vial changes.

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Next steps

Compare online weight loss providersTelehealth platforms prescribing GLP-1 medication, and what each of them actually dispenses — branded pen or compounded vial.Every dosing protocolThe same units-and-volume arithmetic for the other injectables, with the conversion printed rather than assumed.

Related calculators

Educational reference, not medical advice. This converts a dose someone has already prescribed; it never suggests one. Compounded tirzepatide is not FDA-approved and its concentration varies by pharmacy and by vial, so confirm the mg/mL on your own label before drawing, and check any figure here against your prescriber.