GLP-1 Dosing Guide

Last updated: June 2026 · Reviewed June 2026 · Built by the InjectBuddy team

What is the tirzepatide dosing schedule? 2.5–15 mg, week by week

The tirzepatide dosing schedule starts at 2.5 mg once weekly and increases in 2.5 mg steps — 5, 7.5, 10, 12.5, and a maximum of 15 mg — with at least four weeks at each level before advancing. To turn any of those milligram doses into a syringe measurement you divide the dose by your vial's concentration in mg/mL, then multiply the resulting milliliters by 100 to read U-100 units. This guide covers the full titration table, shows the dose-to-units conversion for the most common vial concentrations, and answers the questions people ask most.

Key takeaways: 2.5 mg start, +2.5 mg every 4+ weeks, 15 mg max. Draw volume = dose ÷ concentration. A 10 mg/mL vial keeps every dose between 25 and 150 units; a 2.5 mg/mL vial pushes higher doses past a 1 mL syringe. Always read the mg/mL on your own label. Open the tirzepatide calculator →

The tirzepatide titration schedule

Tirzepatide is a dual GIP and GLP-1 receptor agonist, and like all incretin therapies it is started low and increased slowly so the gut can adapt. The FDA Zepbound label defines 2.5 mg as an initiation dose that is not a maintenance dose, with 5, 10 and 15 mg as the maintenance options. The increment is fixed at 2.5 mg and the interval is "at least 4 weeks on the current dose." The table below shows the textbook climb; in practice a prescriber may hold any step longer if nausea or appetite loss is heavy.

Weeks	Weekly dose	Role
1–4	2.5 mg	Initiation only — not maintenance
5–8	5 mg	First maintenance option
9–12	7.5 mg	Intermediate step
13–16	10 mg	Common maintenance dose
17–20	12.5 mg	Intermediate step
21+	15 mg	Maximum dose

This four-weeks-per-step pattern is the dose-escalation phase used in the pivotal trials: SURMOUNT-1 ran a 20-week escalation to reach 5, 10 or 15 mg in adults with obesity, and SURPASS-2 used the same climb when comparing tirzepatide against semaglutide in type 2 diabetes. Brand pens (Mounjaro, Zepbound) deliver these doses in fixed-volume cartridges; compounded vials leave the milliliter maths to you, which is where concentration matters.

How this is calculated

Two pieces of arithmetic cover every tirzepatide draw. First the volume, then the units:

The two formulas

Draw (mL) = Dose (mg) ÷ Concentration (mg/mL)

Units = Draw (mL) × 100

On a U-100 insulin syringe one unit is 0.01 mL, so multiplying milliliters by 100 gives the unit mark to fill to.

Because concentration sits in the denominator, doubling the vial strength halves both the volume and the unit count for the same dose. That single fact explains why two people on an identical milligram dose can fill their syringes to very different marks.

2.5 mg start · 5 mg/mL vial

2.5 ÷ 5 = 0.50 mL → 0.50 × 100 = 50 units.

2.5 mg = 50 units

5 mg · 5 mg/mL vial

5 ÷ 5 = 1.00 mL → 1.00 × 100 = 100 units — a full 1 mL syringe.

5 mg = 100 units

7.5 mg · 10 mg/mL vial

7.5 ÷ 10 = 0.75 mL → 0.75 × 100 = 75 units.

7.5 mg = 75 units

10 mg · 10 mg/mL vial

10 ÷ 10 = 1.00 mL → 1.00 × 100 = 100 units.

10 mg = 100 units

15 mg max · 10 mg/mL vial

15 ÷ 10 = 1.50 mL → 1.50 × 100 = 150 units. This needs a 1.5 mL or 2 mL insulin syringe.

15 mg = 150 units

Same 7.5 mg dose, weaker vial

7.5 ÷ 5 = 1.50 mL = 150 units — double the 75 units from a 10 mg/mL vial for exactly the same dose.

Concentration, not dose, drives the unit count

15 mg on a 2.5 mg/mL vial (why it fails)

15 ÷ 2.5 = 6.00 mL = 600 units — six full 1 mL syringes. A weak vial is impractical at the top of the ladder.

15 mg = 600 units (avoid)

Dose-to-units chart by vial concentration

The chart below pre-computes every titration step across the three concentrations compounding pharmacies use most. Read down your vial's column; if the result exceeds 100 units you'll need a larger-barrel insulin syringe or a higher-concentration vial.

Dose	2.5 mg/mL	5 mg/mL	10 mg/mL
2.5 mg	1.00 mL · 100 U	0.50 mL · 50 U	0.25 mL · 25 U
5 mg	2.00 mL · 200 U	1.00 mL · 100 U	0.50 mL · 50 U
7.5 mg	3.00 mL · 300 U	1.50 mL · 150 U	0.75 mL · 75 U
10 mg	4.00 mL · 400 U	2.00 mL · 200 U	1.00 mL · 100 U
12.5 mg	5.00 mL · 500 U	2.50 mL · 250 U	1.25 mL · 125 U
15 mg	6.00 mL · 600 U	3.00 mL · 300 U	1.50 mL · 150 U

The same 7.5 mg dose reads 75 units from a 10 mg/mL vial but 150 units from a 5 mg/mL vial — only the concentration changed.

Enter your exact dose and the mg/mL printed on your vial to get the precise draw volume and unit mark.

Tirzepatide Calculator →

Choosing a vial concentration

For the low end of the ladder (2.5–5 mg) almost any concentration is workable. The decision matters at the top: at 12.5–15 mg a 2.5 mg/mL vial demands 5–6 mL — impossible on a single insulin syringe — while a 10 mg/mL vial keeps even the 15 mg maximum at 1.5 mL (150 units). If your pharmacy ships a lower-concentration vial than you expected, your unit count will jump even though the prescribed milligrams are unchanged. Recheck the label every refill.

Side effects and slowing the climb

Nausea, diarrhoea, reduced appetite and fatigue are the common adaptation effects, usually heaviest in the first one to two weeks after each increase. If a step is rough, a prescriber may keep you on the current dose for an extra cycle rather than advancing — the schedule is a guide, not a deadline. The maths above does not change: only your target milligrams do.

So, what is the tirzepatide dosing schedule?

The tirzepatide dosing schedule runs from 2.5 mg once weekly (initiation only) up to a maximum of 15 mg in 2.5 mg increments, with at least four weeks at each step. To find your draw volume, divide the prescribed milligrams by your vial's mg/mL concentration; multiply the result by 100 to read the U-100 unit mark on your syringe. Vial concentration changes the units dramatically — a 7.5 mg dose is 75 units from a 10 mg/mL vial but 150 units from a 5 mg/mL vial — so always verify the mg/mL on your current label. Use the tirzepatide dose calculator to convert any step of the schedule into an exact mL and unit count instantly.

Frequently asked questions

What is the tirzepatide dosing schedule?

Tirzepatide starts at 2.5 mg once weekly and increases in 2.5 mg steps every four weeks or more: 5, 7.5, 10, 12.5, and a maximum of 15 mg. The 2.5 mg dose is initiation only; 5, 10, and 15 mg are the FDA maintenance options.

What is the full tirzepatide dosing schedule from 2.5 mg to 15 mg?

Start at 2.5 mg once weekly for 4 weeks, then increase in 2.5 mg steps no sooner than every 4 weeks: 5 mg, 7.5 mg, 10 mg, 12.5 mg and a maximum of 15 mg. The FDA Zepbound label treats 2.5 mg as initiation only and 5/10/15 mg as maintenance. Your prescriber may hold a dose longer if side effects are pronounced.

How many units is a 7.5 mg tirzepatide dose?

It depends on concentration. From a 10 mg/mL vial, 7.5 divided by 10 = 0.75 mL = 75 units. From a 5 mg/mL vial the same dose is 1.5 mL = 150 units, which exceeds a 1 mL syringe. Read the mg/mL on your own vial first.

Why does my draw volume differ from someone on the same dose?

Draw volume is set by vial concentration, not the dose alone. Two people on 7.5 mg draw 0.75 mL from a 10 mg/mL vial but 1.5 mL from a 5 mg/mL vial. Compounded concentrations vary by pharmacy and batch, so recalculate from your current label rather than copying someone else's unit count.

How does tirzepatide dosing compare with semaglutide?

Tirzepatide is a dual GIP/GLP-1 agonist dosed up to 15 mg weekly; semaglutide is a GLP-1 agonist that tops out at 2.4 mg weekly for weight management. Both titrate slowly and inject once weekly, but tirzepatide's larger milligram doses mean vials are often higher concentration to keep volumes practical.

Medical disclaimer: InjectBuddy is a mathematics and reference tool and does not constitute medical advice. The titration schedule here reflects the FDA-approved branded product; compounded tirzepatide is not FDA-approved and concentrations vary. Always follow the specific dose and concentration your prescriber and pharmacy provide.

Sources

Eli Lilly. Zepbound (tirzepatide) injection — FDA prescribing information. DailyMed, 2024. Source for the 2.5 mg initiation dose, 2.5 mg increments every ≥4 weeks, and 15 mg maximum.
Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387:205–216. 5/10/15 mg doses and the 20-week escalation phase.
Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021;385:503–515. Same escalation used in the head-to-head vs semaglutide.
Garvey WT, et al. Tirzepatide once weekly for obesity in people with type 2 diabetes (SURMOUNT-2). Lancet. 2023;402:613–626. Confirms the titration in a diabetic population.
Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384:989–1002. Source for the semaglutide 2.4 mg weekly comparison.