Retatrutide Weight Loss Calculator
Quick answer: In its phase 2 trial, the highest retatrutide dose (12 mg weekly) produced an average 24.2% body-weight loss at just 48 weeks — around 53 lb for a 220 lb person — with the curve still falling at study end. It is the most potent weight-loss compound ever measured in a trial, and it is NOT yet approved: everything outside Eli Lilly's phase 3 program is unregulated research material.
Projection uses Phase 2 trial averages (48w) — population averages with full titration and lifestyle support. Individual results vary widely; roughly 1 in 7 participants were non-responders.
Retatrutide dose schedule
| Phase | Dose | Notes |
|---|---|---|
| Trial arm 1 | 1 mg weekly | ~8.7% loss at 48 weeks |
| Trial arm 2 | 4 mg weekly | ~17.1% loss at 48 weeks |
| Trial arm 3 | 8 mg weekly | ~22.8% loss at 48 weeks |
| Trial arm 4 | 12 mg weekly | ~24.2% loss at 48 weeks — curve still declining |
What makes a 'triple G' different
Retatrutide agonizes three receptors: GLP-1 (satiety, slower gastric emptying), GIP (fat oxidation, insulin sensitivity) and — the new ingredient — glucagon, which raises resting energy expenditure. Where GLP-1s work almost entirely on the intake side of the energy equation, the glucagon arm pushes the output side too: eat less and burn more, simultaneously.
That third mechanism is why its phase 2 curve kept falling when dual-agonist curves flatten — and why the compound demands more respect: glucagon activity touches heart rate and hepatic glucose handling, the exact parameters phase 3 (TRIUMPH program) is characterizing.
The phase 2 numbers in context
The 2023 NEJM phase 2 results: 24.2% average loss at 48 weeks on 12 mg, with every single participant on the two top doses losing at least 5% — a first in obesity pharmacology. For comparison at similar timepoints, tirzepatide sits around 18-19% and semaglutide around 13-14%. A striking secondary finding: in participants with fatty liver, mean liver-fat reduction exceeded 80%, with most achieving normal liver fat.
Phase 2 caveats apply: smaller samples (n=338), shorter duration, and effect sizes that historically shrink somewhat in phase 3. Even discounted, it likely lands as the most potent option ever approved — if and when it is approved, currently expected no earlier than 2027.
Safety signals worth knowing
The GI profile matches the class (nausea and friends, titration-dependent). The retatrutide-specific finding is a dose-dependent increase in resting heart rate — several beats per minute at higher doses, peaking mid-trial and partially attenuating. Cardiac arrhythmia history is the obvious flag. Skin sensations (tingling) also appeared more than placebo. None of this stopped development; all of it is why 'wait for phase 3' is not just lawyer-speak.
The gray-market reality check
Because the trial numbers are public and the drug is not, retatrutide became the most-hyped compound in the research-peptide market. The honest framing: no approved dosing schedule exists — circulating protocols are reverse-engineered from trial arms; no pharmacy-grade supply exists — purity is whatever your vendor's certificate claims; and no medical monitoring framework exists — trial participants had ECGs and liver panels, gray-market users have vibes.
For those who proceed anyway, the harm-reduction basics are non-negotiable: third-party-tested source, conservative start (0.5-1 mg weekly), slow escalation, and the reconstitution calculator so a 10 mg vial never becomes an accidental 10 mg dose.
Should you wait for it?
If you qualify for treatment today, the pragmatic answer from obesity medicine is usually no — tirzepatide at ~21% is available now with full regulatory backing, and switching later is routine. Chasing an extra projected 3-4 points of loss by entering an unregulated market carries asymmetric risk. The exception people cite is non-response to both approved incretins, where the third mechanism is a genuinely different lever — a conversation for a physician, not a vendor.
FAQ
Is retatrutide approved by the FDA?+
No. It is in phase 3 trials (TRIUMPH program) with approval realistically 2027 at the earliest. Anything sold today is unregulated research material outside any quality or safety framework.
How much more effective is retatrutide than tirzepatide?+
Cross-trial comparison at ~48 weeks: about 24% vs 18-19% average loss. Phase 3 will give the honest number; effects typically shrink a little from phase 2 to phase 3.
What retatrutide dose was used in trials?+
Phase 2 arms were 1, 4, 8 and 12 mg weekly, with starting doses of 2 mg or lower and slow escalation. There is no approved schedule — these are trial parameters, not prescribing guidance.
Does retatrutide raise heart rate?+
Phase 2 showed a dose-dependent resting heart-rate increase of several bpm, attributed to the glucagon mechanism, peaking around week 24 and partially declining after. It's the main signal phase 3 is watching.
Educational content based on published clinical trial data. Projections are population averages, not personal predictions, and nothing here is medical advice — treatment decisions belong with a licensed prescriber. Retatrutide is an investigational compound not approved for use anywhere.