Tirzepatide is dosed once a week, by injection under the skin, and always started low. The Zepbound label sets one starting dose, a fixed step size and a ceiling. [1] The trials that led to approval used the same ladder, and the rest of this page shows where each rung came from.
The weekly doses below are the label's and the trials', not a plan for any one person. How tirzepatide compares with semaglutide in head-to-head trials is covered separately, and the wider weight goal page sets out the other options.
The dose steps on the label
The label states that the starting dose for every indication is 2.5 mg once weekly for 4 weeks [1]. It also states that 2.5 mg is for starting treatment only and is not approved as a maintenance dose.
After 4 weeks the dose rises to 5 mg. From there it may rise in 2.5 mg steps, each after at least 4 weeks on the current dose. The label gives the reason in the same section: the slow climb is there to reduce the risk of stomach and bowel side effects.
| Weekly dose | Earliest start | What the label says it is |
|---|---|---|
| 2.5 mg | Week 1 | Starting dose only, for 4 weeks |
| 5 mg | Week 5 | Maintenance dose for weight |
| 7.5 mg | Week 9 | Step between maintenance doses |
| 10 mg | Week 13 | Maintenance dose for weight or sleep apnea |
| 12.5 mg | Week 17 | Step between maintenance doses |
| 15 mg | Week 21 | Maintenance dose, and the maximum |
The label adds a condition to the ladder. Treatment response and tolerability guide which maintenance dose is chosen, and a lower maintenance dose is an option if a higher one is not tolerated [1]. Climbing to the top is not the default.
Zepbound and Mounjaro: one molecule, two labels
Mounjaro is the same molecule, approved for type 2 diabetes. Its label uses the same 2.5 mg start and the same 2.5 mg steps after at least 4 weeks. [2] The adult maximum is also 15 mg a week. For children aged 10 and older with type 2 diabetes, the Mounjaro label caps the dose at 10 mg.
The Zepbound label carries two indications. For weight reduction the maintenance doses are 5, 10 or 15 mg. For moderate to severe obstructive sleep apnea in adults with obesity, they are 10 or 15 mg [1].
What the SURMOUNT-1 trial gave
SURMOUNT-1 randomized 2,539 adults with obesity, or with overweight and a weight-related condition, and without diabetes [3]. They received 5, 10 or 15 mg once weekly, or placebo, for 72 weeks. The first 20 weeks were a dose-escalation period.
Mean weight change at week 72 was −15.0% on 5 mg, −19.5% on 10 mg and −20.9% on 15 mg. On placebo it was −3.1%. A loss of 20% or more was reached by 50% of the 10 mg group and 57% of the 15 mg group, against 3% on placebo.
The higher doses did not stop more people. Adverse events ended treatment for 4.3%, 7.1% and 6.2% on the three doses, and 2.6% on placebo. The trial ran in people without diabetes, so its figures do not describe the Mounjaro population.
What the sleep apnea trials gave
SURMOUNT-OSA ran two trials in adults with obesity and moderate to severe sleep apnea [4]. Instead of fixed arms, participants took the maximum dose they tolerated, 10 or 15 mg, or placebo, for 52 weeks.
In the trial without CPAP, the apnea-hypopnea index fell by 25.3 events an hour on tirzepatide and 5.3 on placebo. In the trial with CPAP, it fell by 29.3 against 5.5. The label’s 10 or 15 mg maintenance range for sleep apnea mirrors that design [1].
Why the side effects cluster in the early weeks
The label’s pooled weight trials give the size of the problem at each dose [1]. Nausea affected 25%, 29% and 28% of people on 5, 10 and 15 mg, against 8% on placebo. Vomiting affected 8%, 11% and 13%, against 2%.
A later analysis across SURMOUNT-1 to 4 found stomach and bowel side effects in 27.8% to 72.8% of people on tirzepatide, and 12.2% to 32.5% on placebo [5]. Most were not serious, and most began during dose escalation. Between 1.0% and 10.5% of people on tirzepatide stopped because of them.
That same analysis found similar weight loss in people with and without nausea. That matters for anyone who assumes nausea is how the drug works. The authors estimated that these side effects accounted for, at most, 3.1% of the total weight reduction.
Missed doses, timing and pills
The label allows a missed dose to be taken within 4 days. After that, it says to skip the dose and take the next one on the usual day [1]. The weekly day can move, as long as doses stay at least 3 days apart.
The label’s elimination half-life is about 5 to 6 days, and steady levels arrive after about 4 weekly doses. It also warns that tirzepatide slows stomach emptying, which can affect pills taken by mouth. For birth-control pills, it advises a non-oral method or a barrier method for 4 weeks after starting and after each dose increase.
Pens, vials and volumes
Every strength is a different product, not a different amount drawn from one bottle. The single-dose pens and vials hold 0.5 mL at each strength from 2.5 mg to 15 mg [1]. The multi-dose vials and KwikPens hold 2.4 mL, which gives four doses of 0.6 mL each.
So the milligram dose is fixed and the volume depends on the product. Where the pens go, and how to rotate them, is covered in peptide injection sites. Keeping them cold and in date is covered in how to store peptides.
What to take from the label
The label describes a ladder with a fixed start, a fixed step and a fixed top. What it leaves open is how high to climb. The trials show that 5 mg already produced most of the weight loss seen at 15 mg, and that side effects bunch up while the dose is rising.
For the other gut-hormone drugs with trial data behind them, see peptides for weight loss. The dose itself is a decision for you and your prescriber.