The dual GLP-1 / GIP agonist behind Mounjaro and Zepbound — delivering the largest weight-loss results seen in any approved medication to date.
Tirzepatide is a dual agonist that activates both the GLP-1 receptor (like semaglutide) and the GIP receptor (glucose-dependent insulinotropic polypeptide). The combined signal produces greater insulin sensitivity, appetite suppression, and fat loss than single-receptor GLP-1s.
FDA approved as Mounjaro (type 2 diabetes, 2022), Zepbound for chronic weight management (obesity, 2023), and Zepbound for moderate-to-severe obstructive sleep apnea in obesity (December 2024 — the first medication approved for OSA). The SURMOUNT-1 trial (Jastreboff 2022 NEJM, PMID 35658024) showed an average 20.9% body-weight loss at the 15 mg dose using the treatment-regimen estimand (or 22.5% on the efficacy estimand). In the head-to-head SURMOUNT-5 trial (Aronne 2025 NEJM, PMID 40353578), tirzepatide produced ~47% greater relative weight loss than semaglutide 2.4 mg over 72 weeks.
FDA approved as Mounjaro (T2DM) and Zepbound (chronic weight management; OSA in obesity). Prescription-only. After the December 2024 FDA declaratory order resolving the tirzepatide shortage and the expiration of compounding grace periods (Feb 18 2025 for 503A pharmacies, March 19 2025 for 503B outsourcing facilities), large-scale compounding of tirzepatide as “essentially a copy” of approved drugs is no longer permitted; some clinicians prescribe documented variants. Research-peptide markets exist outside the licensed supply chain — purity is not guaranteed. Not WADA prohibited.
Same mechanism as semaglutide: reduces appetite, slows gastric emptying, enhances glucose-dependent insulin release. Provides the core appetite and glycemic control.
GIP enhances fat metabolism and adipose glucose handling. Preclinical data suggest a GIPR-mediated central anti-emetic effect that may partially offset GLP-1’s GI side effects, though human causation is not yet established.
The dual agonism produces greater HbA1c reductions and weight loss than single-receptor GLP-1 agonism in head-to-head trials (SURPASS-2, SURMOUNT-5); whether the effect is additive or synergistic is mechanistically unresolved.
Tirzepatide has one of the most rapidly expanding evidence bases in metabolic medicine — SURPASS (diabetes) and SURMOUNT (obesity) Phase 3 programs covered tens of thousands of patients.
| Benefit | Evidence |
|---|---|
| Weight loss | SURMOUNT-1 (PMID 35658024): ~20.9% body-weight loss at 15 mg over 72 weeks (treatment-regimen estimand) |
| HbA1c reduction | SURPASS program (PMID 34170647 SURPASS-2): HbA1c reduction ~2.0–2.4% at 15 mg in type 2 diabetes |
| Sleep apnea | SURMOUNT-OSA (Malhotra 2024 NEJM, PMID 38912654): mean ΔAHI −25 to −29 events/hour vs ~−5 with placebo |
| Cardiovascular risk | SURPASS-CVOT (Nicholls 2025 NEJM, PMID 41406444): in T2DM with established ASCVD, tirzepatide non-inferior to dulaglutide on 3-point MACE (12.2% vs 13.1%) over median 4 years; not a placebo-controlled CVOT |
| Heart failure | SUMMIT (Packer 2024 NEJM, PMID 39555826): in HFpEF + obesity, CV death or worsening HF event 9.9% vs 15.3% placebo (HR 0.62, p=0.026) over median 104 weeks |
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeEach step is 4 weeks minimum. Extend steps if side effects are significant — do not advance early.
| Weeks | Weekly Dose |
|---|---|
| 1–4 | 2.5 mg |
| 5–8 | 5 mg |
| 9–12 | 7.5 mg |
| 13–16 | 10 mg |
| 17–20 | 12.5 mg |
| 21+ | 15 mg (max) |
Many users stop titrating once they hit a dose that provides satisfying appetite control without side effects — often 5, 7.5, or 10 mg. Max dose isn’t always necessary.
For the FDA-approved OSA indication (Zepbound), labeled maintenance is 10 mg or 15 mg weekly; 2.5 / 5 / 7.5 mg are titration steps only.
Research tirzepatide typically comes as a 10 mg or 30 mg lyophilized vial. Branded Mounjaro/Zepbound pens come pre-filled.
10 mg vial + 2 mL BAC water = 5 mg/mL
| Dose | Volume | Syringe Units |
|---|---|---|
| 2.5 mg | 0.50 mL | 50 units |
| 5 mg | 1.00 mL | 100 units |
| 7.5 mg | 1.50 mL | 150 units (split if needed) |
| 10 mg | 2.00 mL | 200 units |
For higher doses (12.5 & 15 mg) reconstitute with less BAC water (1 mL → 10 mg/mL) to keep injection volume manageable. 10 mg vial at 2.5 mg/week = 4 weeks; at 10 mg/week = 1 week.
Pre-filled with a typical Tirzepatide setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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Tirzepatide has a similar side effect profile to semaglutide, with slightly better GI tolerance at equivalent efficacy (the GIP component appears to reduce nausea).
FDA boxed warning for thyroid C-cell tumors (rodent data). Avoid with MTC or MEN2 history.
Tirzepatide vs. semaglutide?
The 2025 SURMOUNT-5 head-to-head trial (PMID 40353578) in obesity without T2D showed ~20.2% weight loss with tirzepatide vs. ~13.7% with semaglutide at 72 weeks at maximum tolerated doses — a meaningful advantage for tirzepatide, but not the “40% more” often cited in cross-trial comparisons. The earlier SURPASS-2 head-to-head (PMID 34170647) was in T2D vs. semaglutide 1 mg (not 2.4 mg). GI tolerance is similar or slightly better; cash list prices are broadly comparable, though insurance coverage and copay vary.
Sleep apnea benefit?
Worth noting for anyone with comorbid OSA: PMID 38912654 (SURMOUNT-OSA) demonstrated clinically meaningful reductions in apnea-hypopnea index with tirzepatide in patients with moderate-to-severe OSA and obesity.
Do I need to strength train?
Yes — rapid weight loss causes muscle loss. Resistance training 2–3×/week plus 1 g protein per pound lean mass is essential to preserve muscle.
Can I switch from semaglutide to tirzepatide?
Yes. Most clinicians restart at 2.5 mg tirzepatide for 4 weeks, then titrate up. Some start at 5 mg if already established on 1.7+ mg semaglutide.
Can I stop once I’m at goal weight?
Most people regain weight when stopped. SURMOUNT-4 (PMID 38078870) directly quantified this: participants who switched to placebo after 36 weeks of tirzepatide regained ~14% body weight over the following 52 weeks (≈60–67% of the weight they had lost), while those who continued tirzepatide retained ≥80% of their loss. Long-term maintenance dosing (5–10 mg) or a very structured taper with sustained nutrition/training is usually needed.
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Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeYes. Tirzepatide is FDA approved under two brand names: Mounjaro (subcutaneous, type 2 diabetes, approved May 2022) and Zepbound (subcutaneous, chronic weight management approved Nov 2023, plus moderate-to-severe obstructive sleep apnea in adults with obesity added Dec 2024 — the first drug ever approved for OSA in the US). Research-grade tirzepatide sold by peptide vendors is NOT an FDA-approved drug — it is sold only as a research chemical.
Per the FDA label: 2.5 mg/week for 4 weeks (initiation only — not a maintenance dose), then 5 mg/week for at least 4 weeks. Further dose increases of 2.5 mg may be made after at least 4 weeks at the current dose. Available doses: 2.5, 5, 7.5, 10, 12.5, 15 mg once weekly. Maximum dose is 15 mg/week. For the OSA indication, only 10 mg and 15 mg are recognized maintenance doses.
For a 10 mg lyophilized vial, a typical reconstitution is 10 mg + 2 mL of bacteriostatic water, yielding a concentration of 5 mg/mL. A 2.5 mg starting dose draws to 0.50 mL (25 units on a 100-unit insulin syringe). At 15 mg maintenance, the draw is 0.60 mL (60 units on a 100u syringe) from a 30 mg vial reconstituted with 2 mL.
In the head-to-head SURMOUNT-5 trial (N Engl J Med 2025), tirzepatide produced greater weight loss than semaglutide at 72 weeks: approximately 20% mean body-weight reduction on tirzepatide vs. approximately 14% on semaglutide. Tirzepatide currently produces the largest weight-loss results of any FDA-approved medication. Side-effect profiles overlap heavily — both are dual-target dose-dependent GI agents.
Appetite suppression is often noticeable within the first 1–2 weeks. Glycemic improvement (for T2DM) appears within 4 weeks. Weight loss accumulates over months as the dose titrates. In SURMOUNT-1, mean weight loss reached approximately 22.5% on 15 mg/week at 72 weeks.
Per the FDA label, the most common adverse reactions (≥5% of patients) are gastrointestinal: nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain. Most GI events are dose-dependent and attenuate with continued treatment. The label carries a boxed warning for thyroid C-cell tumors based on rodent studies. Pancreatitis and gallbladder events are labeled less-common risks.
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