This page describes how the approved labeling for Mounjaro and Zepbound structures dosing, as published regulatory information. It is not a protocol to follow. Actual dosing is individualized by a prescriber based on response and tolerability, and unregulated "research" vials are not the approved product.
Overview
Tirzepatide dosing follows one pattern across both of its FDA labels: treatment begins at 2.5 mg injected subcutaneously once weekly, the dose is increased in 2.5 mg increments no faster than every 4 weeks, and 15 mg once weekly is the maximum (Mounjaro label, DailyMed). The labels frame 2.5 mg explicitly as a starter dose for treatment initiation, not a dose expected to deliver the full effect. Everything else — how far up a given person titrates, how long they hold at a step, whether they ever reach the maximum — is left to clinical judgment, which is why the same label supports very different real-world regimens.
Why it is dosed weekly
Tirzepatide is a modified peptide carrying a C20 fatty diacid that binds albumin in the bloodstream. That binding protects the molecule from clearance and gives it a half-life of about 5 days, so a single weekly injection keeps receptor exposure continuous (Zepbound label, DailyMed). Two practical consequences follow from that half-life: steady-state levels build over several weeks at any new dose, and the drug's effects — including side effects — take days to fade after the last injection.
How the labels structure dosing
Both labels specify a once-weekly subcutaneous injection (abdomen, thigh, or upper arm) starting at 2.5 mg for the first 4 weeks, then stepwise increases of 2.5 mg with at least 4 weeks at each dose. Zepbound's label designates 5, 10, or 15 mg as maintenance doses for weight management and 10 or 15 mg for obstructive sleep apnea, with 15 mg the maximum for every indication; Mounjaro escalates on the same schedule as needed for glycemic control. Exact titration rules, missed-dose handling, and adjustments for specific situations are set out in the official Mounjaro and Zepbound labeling, which is the authoritative source — not this page.
Notice what the structure implies: reaching the highest dose takes months by design, and the labels direct clinicians to weigh response and tolerability when choosing a maintenance dose rather than defaulting to the maximum. In trials, meaningful results occurred well below 15 mg — SURMOUNT-1's 5 mg arm averaged 15.0% weight loss (Jastreboff et al., NEJM 2022).
Why the dose is stepped up
Gastrointestinal side effects — nausea, vomiting, diarrhea — are dose-related and most frequent when exposure rises. In SURMOUNT-1, GI adverse events clustered during the escalation period and mostly eased afterward (NEJM 2022). The 4-week minimum between steps gives the gut time to adapt at each level before the next increase; clinicians commonly hold a dose longer, or step back down, when a step is not tolerated. Escalating faster than the label allows removes exactly the mechanism that makes the drug tolerable — which is one of the recurring harms reported with self-sourced vials, where nothing enforces the schedule.
Approved product versus research vials
The approved product arrives as single-dose pens or vials containing a pre-measured, verified amount — the dose is fixed at manufacture. Gray-market tirzepatide powder inverts this: the actual content of the vial is unverified, and the delivered dose depends on reconstitution arithmetic and on reading insulin-syringe units correctly, a well-known source of tenfold dosing errors with incretin peptides.
Dosing is also only one part of what a prescription provides. A prescriber screens for the contraindications on the label (personal or family history of medullary thyroid carcinoma or MEN 2), manages interactions with insulin or sulfonylureas, and monitors response — context covered on the side-effects page. For how dosing figured in the clinical results, see the research and evidence overview and the comparison with semaglutide's dosing pattern.