Tirzepatide
Weight Loss, Metabolic Health
In short
- FDA-approved dual GIP and GLP-1 receptor agonist (Mounjaro for diabetes, Zepbound for weight management).
- Head-to-head against semaglutide in SURMOUNT-5, tirzepatide produced greater weight reduction.
- Roughly five-day half-life, dosed once weekly.
- Adding GIP agonism to GLP-1 is the structural difference; the mechanism by which GIP contributes to weight loss is still debated.
- Same gastrointestinal profile and same thyroid C-cell boxed warning as the GLP-1 class.
Structure
How it works
Tirzepatide is a synthetic 39-amino-acid peptide based on the GIP sequence, engineered to activate both the GIP and GLP-1 receptors, with a C20 fatty diacid for albumin binding and weekly dosing.
GLP-1 agonism supplies the familiar effects — glucose-dependent insulin secretion, glucagon suppression, delayed gastric emptying, reduced appetite. The GIP contribution is less settled: GIP receptor agonism appears to improve insulin sensitivity and may reduce nausea relative to GLP-1 alone, which could permit higher effective dosing. Notably, GIP receptor *antagonism* has also shown weight effects, so the pathway is not fully understood.
What the research shows
SURPASS trials in type 2 diabetes showed HbA1c reductions superior to semaglutide 1 mg, insulin degludec, and insulin glargine.
SURMOUNT-1 reported mean weight reduction of about 20.9% at the 15 mg dose over 72 weeks in people with obesity without diabetes.
SURMOUNT-5, a direct head-to-head against semaglutide 2.4 mg, showed roughly 20.2% versus 13.7% mean weight reduction.
As with semaglutide, discontinuation is followed by substantial regain.
Dosing in the literature
Figures below are quoted from published studies, with the species or population they were measured in. They are records of what was studied, not recommendations.
| Studied in | Amount | Route | Source |
|---|---|---|---|
| Human — type 2 diabetes (Mounjaro), approved label | 2.5 mg weekly for 4 weeks, then increase in 2.5 mg steps to a maximum of 15 mg weekly | subcutaneous | FDA label |
| Human — weight management (Zepbound), approved label | Same titration; maintenance 5, 10, or 15 mg weekly | subcutaneous | FDA label |
Commonly reported ranges
These are amounts people report using. They are not from any study, have not been evaluated for safety, and are reproduced here only because they circulate widely and are better seen alongside the evidence than instead of it.
No commonly reported ranges for this compound.
An approved medicine with a published titration schedule. The 4-week minimum interval between escalations exists to limit gastrointestinal effects.
Handling and storage
Supplied as single-dose pens or vials. Weekly, any day, with or without food. Rotate injection sites. If a dose is missed it can be taken within 4 days; otherwise skip it rather than doubling.
Side effects
Nausea, diarrhoea, vomiting, constipation, and reduced appetite dominate, and are dose-related and worst after escalation.
Serious but uncommon: pancreatitis, gallbladder disease, and hypoglycaemia when combined with insulin or sulfonylureas.
Boxed warning for thyroid C-cell tumours from rodent data; contraindicated with personal or family history of medullary thyroid carcinoma or MEN2.
Delayed gastric emptying is relevant to anaesthesia and now appears in pre-operative guidance.
Combinations
Combining with any other incretin agonist duplicates the pathway and compounds gastrointestinal effects without evidence of added benefit.
With insulin or sulfonylureas, those agents typically need reducing to avoid hypoglycaemia.
Combination with bimagrumab and other muscle-preserving agents is under investigation, motivated by the lean-mass loss that accompanies rapid weight reduction.
Research status
SURPASS (diabetes) and SURMOUNT (obesity) programmes, plus SURMOUNT-OSA in obstructive sleep apnoea and SUMMIT in heart failure with preserved ejection fraction. Like semaglutide, this is a genuinely well-evidenced medicine rather than a research compound.
Legal status
FDA-approved and prescription-only in the US, with equivalent status in the EU, UK, Canada, and Australia. Compounded tirzepatide was permitted during the declared shortage; the FDA declared that resolved in 2025.
WADA status
Not currently prohibited by WADA. Verify against the live list before competition.
Conclusion
Tirzepatide currently produces the largest weight reduction of any approved pharmacotherapy, with trial evidence to support it. It sits alongside semaglutide as one of the two compounds here that are properly evidenced medicines.
The practical caveats are the same: titrate slowly, expect gastrointestinal effects, and understand that stopping means regaining.
Sources
- [1]DailyMed — tirzepatide prescribing information (Mounjaro, Zepbound)FDA label
- [2]SURMOUNT-1 — tirzepatide in obesityPubMed
- [3]SURMOUNT-5 — tirzepatide vs semaglutide head-to-headPubMed
- [4]SURPASS programme — tirzepatide in type 2 diabetesPubMed
- [5]PubChem CID 166567236PubChem
- [6]WADA Prohibited List (current)WADA
Track your own Tirzepatide protocol
Peppers logs your doses, models your levels from this half-life, tracks your vials and tells you when you will run out. Free on iPhone.
Reference and educational information only. Not medical advice. Nothing here diagnoses, treats, or prescribes, and nothing here is a recommendation to use any compound. The compounds described are research chemicals and are not approved for human consumption. Legal and anti-doping status change — the review date above is when these claims were last checked. Talk to a qualified clinician about anything you intend to take.