Tirzepatide dosage: the step-up schedule from the label, the maintenance doses studied in trials, and the pharmacokinetics that make once-weekly dosing work.

The short version

Tirzepatide is given by subcutaneous injection (an injection under the skin) once a week. The FDA label for both its type 2 diabetes and obesity indications starts at a low 2.5 mg dose to reduce stomach side effects, then the dose is increased every four weeks until reaching a maintenance level. Maintenance doses in the trials were 5 mg, 10 mg, or 15 mg once weekly. The highest trial dose, 15 mg, produced the largest weight-loss effect: −20.9% of body weight at 72 weeks in SURMOUNT-1. The drug stays in the body for about five days after each injection, which is why once-weekly dosing works. These doses are from the approved prescribing information and published clinical trial protocols — not a recommendation for any individual.

Tirzepatide dosage — the FDA-labeled titration schedule

The tirzepatide dosage schedule used across the SURMOUNT and SURPASS programmes follows a stepwise titration (gradual increase) designed to build tolerance to gastrointestinal side effects before reaching therapeutic maintenance doses. As documented in the FDA prescribing information and in the trial protocols ^[6]:

• Weeks 1–4: 2.5 mg once weekly (starting dose — GI-tolerability period, not a therapeutic maintenance dose)
• Weeks 5–8: 5 mg once weekly
• Weeks 9–12: 7.5 mg once weekly (if well tolerated; otherwise stay at 5 mg)
• Weeks 13–16: 10 mg once weekly (if well tolerated)
• Weeks 17–20: 12.5 mg once weekly (if well tolerated)
• Weeks 21+: 15 mg once weekly (maximum dose; if well tolerated)

The three maintenance doses studied in the SURMOUNT and SURPASS phase 3 trials were 5 mg, 10 mg, and 15 mg once weekly ^[4]. The 20-week escalation period was used in SURMOUNT-1 to reach these maintenance doses. Dose escalation can be slowed if tolerability is an issue; the goal is to reach the highest tolerated dose.

Tirzepatide dose — results by dose level

The dose-response relationship in SURMOUNT-1 was clear and consistent ^[4]:

• 5 mg once weekly: mean body-weight change −15.0% versus −3.1% with placebo at 72 weeks
• 10 mg once weekly: mean body-weight change −19.5% versus −3.1% with placebo at 72 weeks
• 15 mg once weekly: mean body-weight change −20.9% versus −3.1% with placebo at 72 weeks

In SURPASS-2 in type 2 diabetes, HbA1c reduction was also dose-dependent ^[3]:

• 5 mg once weekly: HbA1c −2.01 percentage points at 40 weeks
• 10 mg once weekly: HbA1c −2.24 percentage points at 40 weeks
• 15 mg once weekly: HbA1c −2.30 percentage points at 40 weeks

All three doses were superior to semaglutide 1 mg (which produced −1.86 percentage points) for HbA1c reduction. Body-weight reduction was also greater at every tirzepatide dose versus semaglutide in SURPASS-2 ^[3].

SURMOUNT-MAINTAIN (2026) found that even the 5 mg maintenance dose — the lowest studied — preserved substantial weight reduction to week 112 (−16.6% from baseline) versus −9.9% on placebo (p<0.0001) ^[12].

Tirzepatide injection — route and pharmacokinetics

Tirzepatide injection is administered subcutaneously — under the skin, typically in the abdomen, thigh, or upper arm. This is the only route used in the approved and clinical-trial programme; no oral or intravenous formulations have been approved ^[6].

The fatty-diacid arm of the tirzepatide peptide structure binds albumin (the most abundant protein in blood plasma) in the circulation, dramatically slowing renal clearance and producing an elimination half-life (the time for the drug concentration to fall by half) of approximately five days ^[7]. This extended half-life supports once-weekly dosing and means a steady-state plasma concentration is reached after four to five weeks of weekly injections.

A dedicated clinical pharmacology study found that hepatic impairment did not produce clinically meaningful changes in tirzepatide exposure warranting dose adjustment ^[31]. Population pharmacokinetics across the SURPASS and SURMOUNT programmes have been characterised in peer-reviewed analyses ^[7].

Stored formulations require refrigeration. Clinical-trial product is a subcutaneous solution; formulation-specific reconstitution and storage parameters are outside the scope of the published efficacy literature.

Tirzepatide vs semaglutide — dose comparison context

The semaglutide comparison in SURMOUNT-5 used the maximum tolerated dose of each agent — tirzepatide at 10 or 15 mg and semaglutide at 1.7 or 2.4 mg — in adults with obesity without type 2 diabetes ^[5]. This design is important context for interpreting the dose comparison: SURMOUNT-5 was not a fixed-dose comparison, and participants were only escalated to the highest dose they tolerated. The −20.2% versus −13.7% body-weight result at 72 weeks therefore reflects each drug's achievable maximum in the studied population, not a between-drug comparison at identical titration schedules.

In SURPASS-2 in type 2 diabetes, tirzepatide 15 mg versus semaglutide 1 mg (not the 2.4 mg obesity dose) produced a −5.5 kg greater body-weight reduction at 40 weeks ^[3]. The between-compound difference on HbA1c was smaller (tirzepatide 15 mg −2.30% versus semaglutide 1 mg −1.86%), but still statistically significant at all doses.