# Tirzepatide Dosage: FDA-Labeled Titration Schedule and Pharmacokinetics > Tirzepatide dosage as documented in the FDA label and phase 3 trials: 2.5 mg start, stepwise escalation to a maximum of 15 mg once weekly. Half-life, route, and pharmacokinetics reviewed. ## Before the details Tirzepatide dosage is determined by a prescribing clinician and follows the schedule documented in the FDA label and the phase 3 trial protocols — this page summarises that documented schedule and the pharmacokinetics (how the drug moves through the body) for reference. Tirzepatide is given once weekly as an injection under the skin (subcutaneous injection). The starting dose is low and increases gradually over several months to reduce gastrointestinal side effects. This page does not recommend a dose for any individual; it describes what was studied in the clinical trials and documented in the FDA prescribing label. ## Tirzepatide dosage: the FDA-labeled titration schedule The FDA-approved dosing schedule, as documented in the prescribing information (FDA label, 2022; TIRZEPATIDE-d9b2a150) [3], uses a stepwise escalation to reduce gastrointestinal adverse effects: - Starting dose: 2.5 mg once weekly for 4 weeks - Then: 5 mg once weekly (first maintenance dose, also the lowest studied maintenance dose) - Optional escalation at 4-week intervals: 7.5 mg → 10 mg → 12.5 mg → 15 mg once weekly - Maximum dose: 15 mg once weekly The three maintenance doses used across the SURPASS (type 2 diabetes) and SURMOUNT (obesity) phase 3 programmes were 5 mg, 10 mg, and 15 mg once weekly; the 2.5 mg and 7.5 mg doses are ramp steps only and were not studied as maintenance doses in the pivotal trials [1]. Timeline to maximum dose: approximately 20 weeks when escalating at each available step, though the label allows the dose to remain at any step if the next increment is not tolerated [3]. This schedule is documented in the label; any individual's dosing is a clinical decision made with a prescribing clinician. **Tirzepatide dose in the type 2 diabetes trials (SURPASS):** In SURPASS-2 (n=1879), tirzepatide 5/10/15 mg once weekly produced HbA1c reductions of 2.01/2.24/2.30 percentage points over 40 weeks versus 1.86 percentage points for the comparator [3]. **Tirzepatide dose in the obesity trials (SURMOUNT):** In SURMOUNT-1 (n=2539), tirzepatide 5/10/15 mg once weekly produced mean weight changes of -15.0%/-19.5%/-20.9% over 72 weeks versus -3.1% for placebo [4]. ## Tirzepatide injection: route and administration The tirzepatide injection is subcutaneous — administered under the skin, typically in the abdomen, thigh, or upper arm. This is the only route used in the approved clinical-trial programme; no oral, intravenous, or other form was studied in the phase 3 development programme [1][3]. Rotating injection sites between doses is commonly recommended based on general principles of subcutaneous injection and post-market patient reports of injection site reactions (redness, bruising, mild itching). Formulation details are outside the scope of the published efficacy literature. Marketed formulations are generally refrigerated; specific storage and reconstitution details are in the FDA prescribing information and manufacturer materials. ## What is the half-life of tirzepatide? The half-life of tirzepatide in humans is approximately 5 days [1][46]. This is determined by the fatty-diacid modification on the peptide chain: the C20 eicosanedioic acid arm, attached via a glutamic acid linker and two AEEA units to a lysine side chain, binds albumin (the main protein in blood plasma) with high affinity — effectively extending the time the molecule stays in circulation and enabling once-weekly dosing rather than daily. A phase 1 multiple-ascending-dose study in Japanese adults with type 2 diabetes (Furihata K, et al., Diabetes Obes Metab 2022; PMID 34647404) confirmed the plasma half-life of approximately five days and supported once-weekly administration [46]. A population pharmacokinetics analysis across the phase 3 programme (Pankratz J, et al., CPT Pharmacometrics Syst Pharmacol 2024; PMID 38356317) characterised tirzepatide exposure in detail across the full dose range, supporting the once-weekly schedule [47]. Metabolism and excretion: In a study using radiolabeled tirzepatide in healthy humans (Martin JA, et al., Eur J Pharm Sci 2024; PMID 39243911), renal excretion was the principal elimination route (~66% urine, ~33% faeces); the drug is metabolised via proteolytic cleavage of the amino acid backbone, beta-oxidation of the fatty-diacid moiety, and amide hydrolysis [48]. Hepatic impairment: A clinical pharmacology study (Urva S, et al., Clin Pharmacokinet 2022; PMID 35674880) found hepatic impairment did not produce clinically meaningful changes in tirzepatide exposure warranting dose adjustment [49]. **How long does tirzepatide stay in your system?** Given an approximately five-day half-life, the drug reaches steady-state concentration with weekly dosing after approximately four to five weeks of treatment. After stopping, it would take roughly four to five half-lives (approximately 25 days) for plasma concentrations to fall to low levels — though individual pharmacokinetic variation exists. ## Tirzepatide dosage in older adults A post hoc analysis of pooled SURPASS-1 to -5 data (Rasouli N, et al., Diabetes Ther 2025; PMID 40016573) examined older adults (>=65 years) with type 2 diabetes and without obesity (BMI <30 kg/m2) — a population often underrepresented in major trials. Tirzepatide reduced HbA1c by 1.97–2.10 percentage points across doses in this subgroup, comparable to the overall population response. Weight reduction was dose-proportional but numerically lower than the overall cohort. Hypoglycaemia incidence was consistent with the overall cohort regardless of concurrent insulin or sulfonylurea use [50]. --- The trials are the light; this site is what remains when you chart them honestly.