How many units is 15 mg of tirzepatide?

It depends on exactly one thing: the concentration printed on your vial. Here it is at the 4 strengths compounded tirzepatide usually comes in, and drawn on the barrel.

At 5 mg/mL, 15 mg is 300 units — more than one syringe holds. At 10 mg/mL, 15 mg is 150 units — more than one syringe holds. At 20 mg/mL, 15 mg is 75 units (0.75 mL). At 40 mg/mL, 15 mg is 37.5 units (0.375 mL).

15 mg of tirzepatide, by vial concentration. U-100 insulin syringe.
Vial says	Which is	mL	Units	Syringe
5 mg / 1 mL 10 mg / 2 mL 15 mg / 3 mL	5 mg/mL	3	300 ✗	does not fit in one syringe
10 mg / 1 mL 20 mg / 2 mL 30 mg / 3 mL 50 mg / 5 mL	10 mg/mL	1.5	150 ✗	does not fit in one syringe
20 mg / 1 mL 40 mg / 2 mL 60 mg / 3 mL	20 mg/mL	0.75	75	100-unit
40 mg / 1 mL 80 mg / 2 mL	40 mg/mL	0.375	37.5	50-unit

What that looks like on the barrel

300 units — more than one syringe holds. 3 mL: that's two draws, or a stronger vial.

5 mg/mL → 300 units

150 units — more than one syringe holds. 1.5 mL: that's two draws, or a stronger vial.

10 mg/mL → 150 units

20 mg/mL → 75 units on a 100-unit syringe

40 mg/mL → 37.5 units on a 50-unit syringe

About this dose

Week 21+. The maximum. There is no 17.5. Only two of the common concentrations hold it in one syringe: 20 mg/mL (75 units) and 40 mg/mL (37.5 units). At 10 mg/mL it's 150 units and at 5 mg/mL it's 300 — one and a half, or three, full syringes. Doing two draws for one dose isn't wrong, but a stronger vial makes it one.

Check it yourself

The whole sum is units = dose ÷ concentration × 100. For this dose at 20 mg/mL: 15 ÷ 20 × 100 = 75. If your vial isn't marked in mg/mL, the concentration is the vial's total milligrams divided by the water that went in — a 40 mg vial with 2 mL of water is 20 mg/mL.

Not one of those concentrations?

Tirzepatide vial → unitsU-100 syringe

Vial strength mg

Water you added mL

Your dose mg

Syringe

—

Fill in all three boxes.

Common setups:

← 12.5 mg

Other doses: 2.5 mg · 5 mg · 7.5 mg · 10 mg · 12.5 mg. The whole ladder, with every dose at every strength: the tirzepatide chart. Going the other way — you drew a number of units and want the milligrams — is here. And if the vial isn't tirzepatide at all, mg to units works for anything.