Moving from semaglutide to retatrutide is searched as though a conversion chart existed. None does, and the record explains why. Retatrutide has no label. Its trials keep out anyone who has recently taken a weight-loss medicine. And the one trial that puts retatrutide and semaglutide side by side randomises people to one or the other, so it will compare two starting points, not a switch. This page sets out that trial, the washout arithmetic for semaglutide's long half-life, and the two dose ladders in syringe units.
The single-compound figures are on the semaglutide dosage page and the retatrutide dosage page. The ladders compared without any switch are on retatrutide vs semaglutide, and the same question for the other incretin is on switching from tirzepatide to retatrutide.
The head-to-head trial nobody switches in
TRANSCEND-T2D-2 is the only registered head-to-head efficacy trial of the two; of the 33 retatrutide records on ClinicalTrials.gov, it and one smaller mechanism study are the only ones with a semaglutide arm. It enrolled 1,250 adults with type 2 diabetes whose glucose was not controlled on metformin, with or without an SGLT-2 inhibitor, and randomised them to one of two retatrutide dose levels or to semaglutide. The primary outcome is the change in HbA1c at week 80. The record shows a start date of 21 February 2024 and an actual primary completion date of 27 August 2026; no results were posted on 10 October 2026.
The design matters for this search. Every participant had to be on a stable diabetes regimen and stable weight for 90 days, and anyone who had taken a medicine intended to reduce body weight in that window was excluded. So when the trial reports, it will describe people who started retatrutide or started semaglutide, not people who moved from one to the other.
A second Lilly study, NCT06982859, gives retatrutide, semaglutide or placebo to 95 people with type 2 diabetes to measure insulin secretion and sensitivity at week 28. It too excludes recent use of glucose-lowering drugs outside a short list and of weight-loss medicines in the previous three months, and its primary completion is estimated for January 2027.
The washout arithmetic
Semaglutide clears slowly. Every current Novo Nordisk label gives a half-life of about one week, and WEGOVY's states that semaglutide is present "about 5 to 7 weeks after the last injectable dose of 2.4 mg or 7.2 mg". Retatrutide's phase 1b trial reported a half-life of about 6 days.
| Days after the last semaglutide dose | Semaglutide remaining (7-day half-life) |
|---|---|
| 7 | 50% |
| 14 | 25% |
| 21 | 12.5% |
| 28 | 6.3% |
| 35 | 3.1% |
| 90 | 0.01% |
Ninety days, the trials' exclusion window, is about 12.9 half-lives. Any first retatrutide dose earlier than that adds a GIP, GLP-1 and glucagon receptor agonist to a GLP-1 agonist still circulating. No study has measured the two together in one person, and the half-life figures are worked further on semaglutide's half-life page and retatrutide's half-life page.
Two ladders on different scales
| Step | Semaglutide (WEGOVY label) | Retatrutide (TRIUMPH, company releases) |
|---|---|---|
| Start | 0.25 mg weekly, 4 weeks | 2 mg weekly, 4 weeks |
| Steps | 0.5, 1, 1.7 mg, each 4 weeks | 4, 6, 9 mg, each 4 weeks |
| Maintenance | 1.7 or 2.4 mg | 4, 9 or 12 mg arms |
| Maximum | 7.2 mg | 12 mg |
| Half-life | About 1 week | About 6 days |
The milligram figures belong to different molecules with different receptor targets and different potencies, so a number on one ladder says nothing about a number on the other. Retatrutide's starting dose is eight times semaglutide's in milligrams; that is a fact about two labels' units, not a strength comparison.
The steps as units
Units on a U-100 syringe = mg ÷ mg/mL × 100.
| Amount | 5 mg/mL | 10 mg/mL | 20 mg/mL |
|---|---|---|---|
| Semaglutide 1 mg | 20 units | 10 units | 5 units |
| Semaglutide 2.4 mg | 48 units | 24 units | 12 units |
| Retatrutide 2 mg | 40 units | 20 units | 10 units |
| Retatrutide 4 mg | 80 units | 40 units | 20 units |
| Retatrutide 12 mg | 240 units | 120 units | 60 units |
The error this move invites is carrying a unit count across vials. Twenty-four units from a semaglutide vial at 10 mg/mL is 2.4 mg; the same 24 units from a retatrutide vial at 5 mg/mL is 1.2 mg of a different drug. The mg to units page sets out the formula, semaglutide in units works that molecule both ways, and the retatrutide calculator setting works any retatrutide vial.
What is not established
No label, trial, case series or pharmacokinetic study covers moving from semaglutide to retatrutide; the one head-to-head trial had not reported on 2026-10-10 and does not study a switch; no dose equivalence between the molecules exists in the record. Retatrutide is unapproved. Nothing on this page is a starting dose, an interval or a plan. The compounds are covered in Medibact's Semaglutide guide and Retatrutide guide; those decisions belong with a physician.
Sources and dates
Opened 2026-10-10: ClinicalTrials.gov v2 records for the 33 retatrutide studies, read for semaglutide arms and prior-medicine rules, including NCT06260722 (TRANSCEND-T2D-2) and NCT06982859 in full; the PubMed search described above (2 records, both reviews). Carried from this site's pages with their read dates: the semaglutide half-life and WEGOVY persistence statements (semaglutide half-life page, 2026-09-26), the WEGOVY ladder and 7.2 mg maximum (Wegovy dose chart, 2026-10-06), the retatrutide half-life (Urva et al., The Lancet 2022, PMID 36354040) and the TRIUMPH escalation from Lilly's releases (retatrutide page, 2026-09-18). Remaining shares and units are arithmetic by this site. Corrections go to the contact page.