# Tirzepatide Dosing — FDA-label titration schedule and pharmacokinetics > An editorial summary of how tirzepatide is dosed: the 2.5 mg starting dose, the 4-week titration intervals, the maintenance doses, and the pharmacokinetic profile. Not medical advice. Tirzepatide is dosed once weekly by subcutaneous injection. The FDA label specifies a six-step titration; here is what each step is, and why. ## What the titration schedule means in plain terms Tirzepatide is dosed once weekly by subcutaneous (under-the-skin) injection. The approved starting dose — 2.5 mg — is too low to have a meaningful effect on blood sugar or body weight; it exists purely to let the digestive system adjust before higher doses are introduced. Every four weeks the dose steps up: 5 mg, then 7.5 mg, then 10 mg, then 12.5 mg, then up to 15 mg at the top. The 2.5 mg start and slow climb are intentional — nausea, the drug's most common side effect, is worst during dose increases and tends to fade once a stable dose is reached. Most of the weight-loss and blood-sugar benefit in the trials came at the 10 mg and 15 mg maintenance doses, though some people do well at 5 mg. This page summarises what the FDA label specifies and why the slow escalation is built into the design. ## The FDA-labeled titration schedule Every tirzepatide indication uses the same titration concept: start low to blunt gastrointestinal side effects, then step up every four or more weeks until either the target maintenance dose is reached or the maximum tolerated dose is established [12]. The label-specified schedule is: - **Weeks 1-4:** 2.5 mg once weekly (initiation dose; not for glycemic or weight-management efficacy — this exists purely to prepare the gut for the higher doses). - **Weeks 5-8:** 5 mg once weekly. This is the lowest dose with documented efficacy in SURPASS and SURMOUNT. - **Weeks 9-12:** 7.5 mg once weekly (an intermediate step if titrating further). - **Weeks 13-16:** 10 mg once weekly. A common maintenance dose, particularly for type 2 diabetes patients with modest weight goals. - **Weeks 17-20:** 12.5 mg once weekly. - **Weeks 21+:** 15 mg once weekly — the maximum approved dose, used in most SURMOUNT obesity trials and in SURMOUNT-OSA [3][5]. The label permits remaining at any tolerated dose if a patient does not need to escalate further. It also permits going back down a step if a higher dose is poorly tolerated. The titration interval is described as 'at least 4 weeks' — slower titration is permitted [12]. ## Why the slow start matters Across both the SURPASS and SURMOUNT programs, gastrointestinal adverse events — nausea, diarrhea, vomiting, constipation — were the most common reasons participants discontinued. The incidence was highest during titration and decreased as patients reached their maintenance dose [20]. In a pooled SURPASS analysis, severe gastrointestinal events occurred in 1.7% of patients on 5 mg, 2.5% on 10 mg, and 3.1% on 15 mg, versus 1% on placebo [20]. The FDA label explicitly attributes the dose-escalation schedule to gut tolerance, not to plateauing efficacy. ## Pharmacokinetics Tirzepatide has an apparent elimination half-life of approximately 5 days (~116-120 hours) in humans. Peak plasma concentration occurs 24-72 hours after a subcutaneous injection. Steady state is reached after roughly four weeks of weekly dosing [11]. The long half-life is engineered into the molecule. A C20 fatty diacid (eicosanedioic acid) is attached at Lys20 via a γGlu-2xAEEA linker. Once injected, this tail binds tightly to circulating serum albumin — over 99% of the drug is albumin-bound — which shields the peptide from renal filtration and proteolytic degradation [10][13]. The same trick is used in semaglutide and in newer fatty-acid-conjugated insulins. Injection sites studied in registration trials include the abdomen, thigh, and upper arm. The label recommends site rotation but does not require a specific site [12]. ## Storage and handling Tirzepatide is supplied in single-dose pens at refrigerated temperatures (2-8°C / 36-46°F). The current FDA label permits room-temperature storage up to 30°C (86°F) for up to 21 days; pens exposed to temperatures above 30°C should be discarded [12]. The drug is dosed once weekly on the same day each week. The label permits switching the day of administration as long as at least three days separate two doses [12]. ## Maintenance dose by indication - **Type 2 diabetes:** 5, 10, or 15 mg, individualized for glycemic goals and tolerance. - **Chronic weight management:** 5, 10, or 15 mg, generally titrated to the maximum tolerated dose for weight-loss magnitude. - **Obstructive sleep apnea with obesity:** 10 or 15 mg only — the lower doses were not studied for this indication. These summaries are not a substitute for the FDA-approved prescribing information or for clinical judgment. We report what the trials and label say; we do not recommend doses for any specific person. --- An independent editorial chronicle of the clinical literature — not a clinic, not a vendor, not a prescription.