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CompareTirzepatide

The dual GIP/GLP-1 agonist behind Mounjaro and Zepbound.

Retatrutide

Eli Lilly's investigational triple-hormone agonist: GIP, GLP-1 and glucagon in one weekly shot.

CategoryMetabolic & WeightMetabolic & Weight
Evidence 5/5FDA-approved on the basis of large phase 3 programs (SURPASS for diabetes, SURMOUNT for obesity, SURMOUNT-OSA for sleep apnea). 4/5Large phase 2 RCT (NEJM 2023) and multiple positive phase 3 trials (TRIUMPH program). Not yet approved, and long-term safety data is still being collected.
FDA statusFDA-approved (Mounjaro 2022, Zepbound 2023)Not FDA-approved (phase 3)
WADA (sport)Not prohibitedNot prohibited
Also known asMounjaro, Zepbound, LY3298176, AMP-2 (TR)LY3437943, AMP-3 (RT), GGG tri-agonist, "Reta"
How it worksA 39-amino-acid peptide with a C20 fatty diacid at lysine-20 that binds albumin, so it lasts about 5 days. GLP-1 and GIP receptor activation lowers appetite, slows stomach emptying, and boosts insulin release when blood sugar is high.A 39-amino-acid peptide with a C20 fatty-acid chain that binds albumin, giving it a long half-life. It activates GIP and GLP-1 receptors (appetite, insulin release, slower stomach emptying) like tirzepatide, and adds glucagon-receptor activity, which is thought to raise energy use and reduce liver fat.
Half-lifeAbout 5 days (once-weekly dosing)About 6 days (once-weekly dosing)
Commonly reported doses
  • Label start: 2.5 mg, once weekly
  • Label maintenance (low): 5 mg, once weekly
  • Label maximum: 15 mg, once weekly
  • Trial-style titration (start): 2 mg, once weekly
  • Community-reported low start: 1 mg, once weekly
  • Trial maintenance (top dose): 12 mg, once weekly
RouteSubcutaneous (abdomen, thigh, upper arm)Subcutaneous
Good once mixed~28 days in the fridge~28 days in the fridge
Top side effects
  • Nausea, diarrhea, vomiting, constipation (most common, worst during dose increases)
  • Reduced appetite, indigestion, belly pain
  • Injection-site reactions
  • Nausea, diarrhea, constipation, vomiting (most common, dose-related)
  • Reduced appetite
  • Raised resting heart rate (seen in trials, dose-related)
Lowest price per mg$1.10 (60 mg vial, 40% off)$4.00 (30 mg vial, 40% off)
Latest lab purity99.76% (lot TRZ0001)99.92% (lot RT0004)
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