Quick answer: in phase 2 trials, retatrutide dosage ranged from 0.5 mg to 12 mg injected once a week, with the higher doses reached gradually from a 2 mg or 4 mg starting dose.[1][2] Weight loss rose with dose up to 8 mg and then leveled off, while gastrointestinal side effects also increased with dose. Retatrutide is an investigational drug, and these are research doses, not a treatment plan.
This guide covers what each trial tested and what happened at each dose. For the bigger picture, see our retatrutide profile and the latest peptide news.
Doses tested in the phase 2 obesity trial
The obesity trial enrolled 338 adults with a BMI of 30 or more, or 27 or more with a weight-related condition, and treated them for 48 weeks.[1][3]
| Group | Starting dose | Target (maintenance) dose |
|---|---|---|
| 1 mg | 1 mg | 1 mg |
| 4 mg | 2 mg or 4 mg | 4 mg |
| 8 mg | 2 mg or 4 mg | 8 mg |
| 12 mg | 2 mg | 12 mg |
| Placebo | — | — |
Weight loss by dose
The primary result was the percentage change in body weight at 24 weeks, with 48-week results as a secondary measure.[1]
| Dose | Change at 24 weeks | Change at 48 weeks |
|---|---|---|
| 1 mg | −7.2% | −8.7% |
| 4 mg | −12.9% | −17.1% |
| 8 mg | −17.3% | −22.8% |
| 12 mg | −17.5% | −24.2% |
| Placebo | −1.6% | −2.1% |
At 48 weeks, 83% of people on 12 mg had lost at least 15% of their body weight, compared with 2% on placebo.[1]
Doses tested in the type 2 diabetes trial
The diabetes trial enrolled 281 adults with type 2 diabetes and compared retatrutide maintenance doses of 0.5 mg, 4 mg, 8 mg and 12 mg against placebo and dulaglutide 1.5 mg.[2][4]
At 24 weeks, HbA1c fell by 2.02 percentage points on the 12 mg dose, versus 1.41 on dulaglutide and almost no change on placebo. Body weight at 36 weeks fell by 16.94% on 12 mg.[2]
Side effects by dose
In both trials, the most common side effects were gastrointestinal: nausea, diarrhea, vomiting and constipation.[1][2]
- They were dose-related and mostly mild to moderate.
- In the diabetes trial they ranged from 13% of people on 0.5 mg to 50% on the fast-escalation 8 mg dose.[2]
- In the obesity trial, a lower 2 mg starting dose partially reduced them compared with starting at 4 mg.[1]
- Heart rate rose with dose, peaked at 24 weeks and then declined.[1]
What this means for you
These numbers come from controlled trials with medical supervision, screening and follow-up. Retatrutide had not been approved by the FDA as of our last review, so there is no official prescribing dose yet. Talk to a licensed clinician before making any decision about a weight-loss medication.