1. What is retatrutide?
An investigational once-weekly injectable peptide developed by Eli Lilly that activates GIP, GLP-1, and glucagon receptors. It is in Phase III trials and has not been approved in any country.
2. How much weight can people lose on retatrutide?
In the published Phase II trial, the 12 mg group lost 24.2% at 48 weeks. Lilly’s unpublished Phase III summaries show 20.8% to 28.7% at 68 to 80 weeks.
3. Is retatrutide better than tirzepatide?
Unknown. No head-to-head trial has been conducted. Indirect comparisons suggest retatrutide may be more effective for weight loss, but it also has the highest adverse event rate.
4. What is the retatrutide dose?
Trials used 4 mg, 9 mg, or 12 mg once weekly, starting at 1 to 2 mg and escalating every four weeks. Outside trials, there is no validated effective dose.
5. How much bacteriostatic water for 30 mg retatrutide?
3 mL yields 10 mg/mL. On a U-100 insulin syringe, 1 mg equals 10 units. Use a reconstitution calculator to verify your own numbers.
6. What are the side effects of retatrutide?
Nausea, vomiting, diarrhea, and constipation are most common. Heart rate increases. Seven percent of trial participants reported skin sensitivity. Rare pancreatitis and gallbladder events have been recorded.
7. Does retatrutide cause liver damage?
Trials found no liver toxicity signal. Six cases of acute liver injury have been linked to gray-market products labeled retatrutide, with suspicion falling on a contaminant rather than the compound itself.
8. Is retatrutide legal?
It has not been approved in any country for human use and cannot be compounded under U.S. law. Lilly plans to file with the FDA in Q1 2027.
9. Is retatrutide banned by WADA?
It is not on the 2026 prohibited list. GLP-1 receptor agonists have been added to WADA’s 2026 monitoring program, meaning use is being tracked before any decision is made.
10. When will retatrutide be approved?
Lilly says it will file with the FDA in Q1 2027. Under standard timelines, an FDA decision would come in late 2027 or 2028.
Conclusion
Retatrutide has a clear mechanism and striking data, but it remains pre-approval. Understanding its mechanism, evidence, and risks matters more than chasing hype.