Retatrutide's trials have treatment durations, not cycles: every protocol on ClinicalTrials.gov gives it once weekly without planned breaks for a fixed period — 48 weeks in phase 2 and 80 weeks in the main phase 3 trials (registry read 2026-11-03). "Cycle", the word in the search, comes from the way other research peptides are discussed online, with weeks on and weeks off. This page sets out how long each retatrutide trial ran, the one trial built to measure stopping, and what a course adds up to in milligrams. It reports; it recommends no duration.
How cycle language arose for peptides in general, and which compounds have any labelled break, is on peptide cycle length. The doses within each trial are on the retatrutide dose schedule.
How long each trial runs
| Trial (registry) | Participants | Length (time frame of the primary result) | Status, 2026-11-03 |
|---|---|---|---|
| Phase 2 obesity (NCT04881760) | 338 | 48 weeks; primary result at 24 | Completed, results posted |
| TRIUMPH-1 (NCT05929066) | 2,335 | 80 weeks; extension to 104 for BMI ≥35 | Completed; sponsor topline 2026-05-21 |
| TRIUMPH-2 (NCT05929079), type 2 diabetes | 1,152 | 80 weeks + 4 weeks off-treatment follow-up | Completed; topline 2026-07-23 |
| TRIUMPH-3 (NCT05882045), cardiovascular disease | 1,946 | 80 weeks | Completed; topline 2026-07-23 |
| TRIUMPH-4 (NCT05931367), knee osteoarthritis | 445 | 68 weeks | Completed |
| TRIUMPH-5 (NCT06662383), against tirzepatide | 800 | 80 weeks | Active; completion est. 2026-11 |
| TRIUMPH-6 (NCT06859268), maintenance | 643 | to week 116 | Active; completion est. 2028-04 |
| TRIUMPH-7 (NCT07035093), low back pain | 586 | up to 72 weeks | Active |
| TRIUMPH-8 (NCT07232719) | 250 | 56 weeks | Active |
| TRIUMPH-9 (NCT07357415) | 600 | 104 weeks | Active |
| Cardiovascular and kidney outcomes (NCT06383390) | 10,000 | to study end, about 248 weeks | Active; completion est. 2029-02 |
Participant counts are the registry's enrolment figures; Lilly's releases give 2,339 randomised for TRIUMPH-1 and 1,949 for TRIUMPH-3. The longest completed exposure reported so far is TRIUMPH-1's 104-week extension, in which, by Lilly's release, participants continuing on 12 mg had lost an average of 30.3%.
The one trial built to measure stopping
TRIUMPH-6 is the retatrutide equivalent of the tirzepatide and semaglutide withdrawal trials. Its registry record lists three arms after a lead-in on "Retatrutide Dose 1": continue on it, move to "Dose 2", or switch to placebo, with percent weight change measured from week 0 to week 116. Until it reports — primary completion is estimated for April 2028 — there is no controlled answer to what happens to weight when retatrutide stops.
The related molecules have that answer. When tirzepatide was replaced by placebo in SURMOUNT-4, weight rose 14.0% over 52 weeks; when semaglutide was replaced in STEP 4, it rose 6.9% over 48 weeks. Both trials, and the off-treatment extension of STEP 1, are set out on the tirzepatide and semaglutide maintenance page. Whether retatrutide behaves the same way, given its additional glucagon-receptor activity, is exactly the question TRIUMPH-6 is designed to test.
What a course adds up to
Eli Lilly's releases describe the phase 3 ladders: a 2 mg start, a step every four weeks, and target doses of 4 mg (one step at 2 mg in TRIUMPH-1), 9 mg (via 2, 4 and 6 mg) and 12 mg (via 2, 4, 6 and 9 mg). Assuming every weekly dose is given, an 80-week course adds up as follows:
| Arm | Escalation weeks | Milligrams during escalation | Weeks at target | Total over 80 weeks | 10 mg vials |
|---|---|---|---|---|---|
| 4 mg | 4 | 8 mg | 76 | 312 mg | 31.2 |
| 9 mg | 12 | 48 mg | 68 | 660 mg | 66 |
| 12 mg | 16 | 84 mg | 64 | 852 mg | 85.2 |
At 10 mg/mL, the target doses are 40, 90 and 120 units on a U-100 syringe; the 12 mg dose is more than one 1 mL syringe at that concentration and 60 units at 20 mg/mL. How many doses a single vial gives at each concentration is on the doses-in-a-vial guide, and the unit tables are on retatrutide units.
Half-life and the end of a course
The phase 1b study reported a half-life of about 6 days (Urva et al., The Lancet 2022, PMID 36354040). By simple arithmetic, about 45% of the last dose remains a week after it, about 20% after two weeks and under 10% after three, so the drug's effect does not stop on the day of the last injection. The full calculation is on retatrutide half-life.
What is not established
Whether weight returns after retatrutide stops, and how fast: unreported until TRIUMPH-6. Whether planned breaks change anything: never tested. What happens beyond 104 weeks: the cardiovascular outcomes trial will be the first long record. Eli Lilly's July 2026 release states that retatrutide "cannot be legally sold or marketed for human use" and that the company plans to apply to the FDA in the first quarter of 2027. Medibact's retatrutide guide covers the compound. Decisions about any medicine belong with the prescriber.
Sources and dates
Opened 2026-11-03: the ClinicalTrials.gov v2 API records NCT04881760, NCT05929066, NCT05929079, NCT05882045, NCT05931367, NCT06662383, NCT06859268, NCT07035093, NCT07232719, NCT07357415 and NCT06383390 (arms, enrolment, primary outcome time frame, status); Eli Lilly's TRIUMPH releases of 2026-05-21 and 2026-07-23 (PR Newswire); the abstracts of PMIDs 36354040, 38078870 and 33755728 through NCBI E-utilities. Course totals, vial counts, unit and half-life arithmetic by this site. Corrections go to the contact page.