What is the retatrutide dosage?
Retatrutide has no FDA-approved dose, because retatrutide isn’t FDA approved. What exists instead is a set of doses that Eli Lilly’s investigators gave to supervised participants in clinical trials: a once-weekly injection, started low at 2 mg, stepped up roughly every four weeks, and capped at 12 mg — the highest dose studied in the published obesity work.
That distinction matters more here than on any other page on this site. A dosage page for an approved drug describes an FDA label. This one describes a research protocol. Nobody in the US can lawfully write you a retatrutide prescription today, so there is no dose for you to be on.
| Dose | When | Notes |
|---|---|---|
| 2 mg | Trial starting dose | Investigational, schedule set by trial protocol, not an FDA label |
| 4 mg | Escalation | Stepped up monthly in trials |
| 8 mg | Escalation | Mid-range dose studied |
| 12 mg | Highest studied | Produced the largest weight loss in Phase 2 |
Why there’s no retatrutide dosing guide
An approved drug’s dosing schedule is the end product of a long process: trials establish the dose–response curve, the FDA reviews the safety data behind every step, and the agency approves specific strengths with specific escalation rules. Retatrutide is still inside that process — in Phase 3, the last stage before a company can even apply.
Until that finishes, three things simply don’t exist:
- An approved starting, maintenance, or maximum dose. Trial doses are chosen to answer research questions, and some arms exist specifically to test whether a dose is too high.
- A prescriber who can supervise you on it. In trials, dose changes happen alongside scheduled labs, weigh-ins, and adverse-event reporting.
- A verified product to dose. A schedule is meaningless if you can’t confirm what’s in the vial — see where to buy retatrutide for why that’s the harder problem.
How the trial escalation worked
Retatrutide’s trials followed the same logic every drug in this class uses: start well below the effective dose, climb slowly, and let the digestive system adapt. In the Phase 2 obesity study, participants began at a low weekly dose and moved up in steps at roughly four-week intervals until they reached their assigned target — 1, 4, 8, or 12 mg once weekly (⚠ verify the exact arm structure and starting-dose sub-arms against the NEJM report).
The pace is the point. Nausea, vomiting, and diarrhea cluster around each increase across every GLP-1-class drug, and the escalation ladder exists to blunt that. Trials also ran two different starting doses into the same target dose to test whether a gentler ramp improved tolerability (⚠ verify).
What each dose produced
Weight loss tracked with dose across the Phase 2 study, and unlike some drugs in this class the curve had not clearly flattened by the top dose — one reason the 12 mg arm drew so much attention.
| Weekly dose | Average weight change at 48 weeks |
|---|---|
| Placebo | about −2% |
| 1 mg | ⚠ verify |
| 4 mg | ⚠ verify |
| 8 mg | ⚠ verify |
| 12 mg | −24.2% (~58 lb) |
The 12 mg figure comes from the published Phase 2 results and is the number behind every headline about retatrutide. The intermediate arms are flagged pending verification against the primary report — we’d rather leave a cell blank than publish a trial number we haven’t checked. Full context on the outcomes is on the retatrutide before-and-after page.
Phase 3 dosing (TRIUMPH)
Lilly’s Phase 3 program, TRIUMPH, carries the same once-weekly design and the same 12 mg ceiling into larger and longer studies — including TRIUMPH-1 in obesity and TRIUMPH-4 in obesity with knee osteoarthritis (⚠ verify the current dose arms and durations against the ClinicalTrials.gov records; Phase 3 details can change mid-program).
If retatrutide is eventually approved, the label’s schedule will be derived from these trials but won’t necessarily match them. Approved schedules routinely differ from the research protocol — the FDA can approve a narrower dose range, a slower ramp, or fewer strengths than were studied. Treat today’s trial numbers as provisional.
About the dosing charts circulating online
The gap isn’t arithmetic — it’s everything the arithmetic assumes. A milligram figure only means something if the vial’s identity, purity, and concentration are verified, and no one is verifying grey-market vials. That’s a different and larger risk than any side effect documented in the trials themselves.
If you want a dose you can actually be prescribed
The approved dual and single agonists have published, FDA-reviewed schedules, and a licensed prescriber can start you on one. Tirzepatide runs 2.5 mg to 15 mg once weekly; semaglutide runs 0.25 mg to 2.4 mg once weekly on the weight-management label. Both have something retatrutide doesn’t: a dose someone is accountable for.
Retatrutide: the complete guide How the triple agonist works, trial results, the approval timeline, and how to join a trialThis page is informational and is not medical advice. Retatrutide is an investigational drug that is not approved by the FDA and cannot be legally prescribed or sold in the US. Nothing here is a dosing recommendation. See our medical disclaimer.