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12.5 units of tirzepatide is how many mg

You are trying to work out how much to draw or when to step up.

Reference and calculator, not medical advice. Dosing figures below are transcribed from FDA-approved prescribing information and link back to it. Last reviewed August 2026.

12.5 units is a mark on the syringe, not a dose. What it equals in milligrams depends entirely on the concentration of the vial you drew from — the same 12.5 units can be several different doses. The table below runs the conversion at each concentration tirzepatide is commonly supplied at.

12.5 units = how many mg?

Reverse conversion: mg = (units ÷ 100) × concentration. U-100 syringe assumed.

If your vial is12.5 units equalsVolumeClosest labelled step
5 mg/mL0.63 mg0.13 mL2.5 mg
10 mg/mL1.25 mg0.13 mL2.5 mg
20 mg/mL2.50 mg0.13 mL2.5 mg (exact)

Notice how far apart these rows are. 12.5 units is not a dose until you know the concentration — quoting units without it is meaningless and is how dosing errors happen.

Zepbound titration schedule

Tirzepatide · once weekly · subcutaneous injection · as published in the prescribing information

StepDoseNotes
Weeks 1–42.5 mgStarting dose — not intended for weight loss effect
Weeks 5–85 mg—
Weeks 9–127.5 mg—
Weeks 13–1610 mg—
Weeks 17–2012.5 mg—
Week 21+15 mgMaximum dose

This is the labelled default. Holding at a step longer than shown is common practice and is a decision for your prescriber. Transcribed from the Zepbound prescribing information (label revised 6 May 2026); checked against that label on 7 August 2026.

mg → syringe units converter

U-100 syringe. Formula: (dose ÷ concentration) × 100.

12.5units on a U-100 syringe
= 0.125 mL  ·  2.5 mg at 20 mg/mL

Check the concentration printed on the vial you are actually holding. The same dose in milligrams is a completely different mark on the syringe at a different concentration. If the number here does not match what your prescriber told you, trust your prescriber.

This is the single most common place people go wrong. A dose given to you in units is only meaningful alongside the concentration it was calculated for — if you switch vials and the concentration changes, the same number of units is a different dose.

The one number that does not travel is the one on the syringe. A dose in milligrams means the same thing everywhere; 12.5 units means whatever the concentration in front of you makes it mean. Carry the milligrams between vials and recalculate the units each time.

Common questions

What is the starting dose of Zepbound?
The prescribing information lists 2.5 mg once weekly as the starting dose, held for the first four weeks before any increase.
What is the maximum labelled dose of Zepbound?
15 mg once weekly, reached through the stepped schedule shown above.
How many units is 5 mg at 20 mg/mL?
25.0 units on a U-100 syringe. The arithmetic is (dose ÷ concentration) × 100, and it only holds if the concentration on your vial matches.

Sources and last review

Every dosing figure on this page is transcribed from an FDA-approved label and links back to it. Conversions are arithmetic you can repeat by hand. Nothing here is reviewed by a clinician, and this site does not employ one — which is exactly why what I do publish stays traceable to its source.

Transcribed from the labels above and checked by me — Gavin, who builds this site, takes a GLP-1, and is not a clinician. Last reviewed August 2026. Found an error? [email protected] — I treat corrections as bugs. How this site is built and funded.

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