Retatrutide vs Semaglutide Dosage: Equivalent Dose Conversion Guide

Why Dose Conversion Is Not Straightforward

Converting between retatrutide and semaglutide doses is not a simple ratio because the drugs have different mechanisms, different receptor affinities, and different pharmacokinetic profiles. Semaglutide activates only the GLP-1 receptor at maximum doses of 2.4 mg weekly for weight loss. Retatrutide activates three receptors and is dosed up to 12 mg weekly. The drugs are not equivalent milligram for milligram, and there is no validated conversion chart because no head-to-head trials have established bioequivalence between specific doses of each drug.

Estimated Equivalent Doses Based on Efficacy

Based on cross-trial comparisons, semaglutide 2.4 mg weekly produces approximately 14.9% weight loss at 68 weeks, while retatrutide 4 mg produces approximately 15-17% weight loss at 48 weeks in the Phase 2 data. This suggests that retatrutide 4 mg is roughly equivalent to semaglutide 2.4 mg in terms of weight loss efficacy. Retatrutide 8 mg produces 20-22% weight loss, which no dose of semaglutide can match. Retatrutide 12 mg produces 24-28% weight loss. These are estimates based on cross-trial comparisons, not direct head-to-head data, and individual responses vary significantly.

Switching from Semaglutide to Retatrutide

For someone currently using semaglutide who wants to switch to retatrutide, the safest approach is to start retatrutide at the lowest dose — 2 mg weekly — regardless of the semaglutide dose being used. This allows the body to adapt to the triple-agonist mechanism without assuming tolerance from single-receptor activation. The graduated titration schedule should be followed even if the semaglutide dose was high. There is no data on switching directly from semaglutide to retatrutide, so a conservative approach is warranted until clinical experience accumulates.