Retatrutide Dosage: A Complete Guide
Retatrutide is one of the most searched weight loss medications right now, and dosage is the number one question we hear about it. This guide explains the doses used in clinical trials, how those doses were increased, what results people saw, and what to know before you consider it.
Important: Retatrutide is not FDA-approved. The doses below come from clinical trials. They are not instructions for using it on your own.
What is retatrutide?
Retatrutide is a once-weekly injection made by Eli Lilly. It acts on three hormone receptors: GIP, GLP-1, and glucagon. Semaglutide acts on one of these and tirzepatide acts on two. The glucagon piece may help the body burn more energy, which is one reason researchers are so interested in it. Read more in What Is Retatrutide?
Where retatrutide stands with the FDA
As of October 2026, retatrutide is still investigational. In July 2026, Lilly reported positive results from two large phase 3 trials and said it plans to ask the FDA for approval in the first quarter of 2027. Until it is approved, it is not available as a prescription medication from a regular pharmacy.
Retatrutide doses studied in clinical trials
Phase 2 trial
The phase 2 obesity trial, published in 2023, tested once-weekly doses of 1 mg, 4 mg, 8 mg, and 12 mg over 48 weeks. Average weight loss at 48 weeks was:
1 mg: about 9%
4 mg: about 17%
8 mg: about 23%
12 mg: about 24%
Placebo: about 2%
Phase 3 trials
The larger phase 3 trials, called TRIUMPH, tested 4 mg, 9 mg, and 12 mg once weekly for 80 weeks.
Adults with type 2 diabetes and excess weight: about 13% weight loss at 4 mg, 19% at 9 mg, and 21% at 12 mg, compared with 4% on placebo.
Adults with severe obesity and heart disease: about 22% weight loss at 9 mg and 23% at 12 mg, compared with about 3% on placebo.
These are averages. Some people lost much more and some lost much less.
How the dose was increased in trials
Nobody in the trials started at the full dose. Participants began low, often at 2 mg, and the dose was raised in steps about every four weeks until they reached their assigned dose. Going slowly gives the stomach time to adjust and lowers the chance of nausea and vomiting. This step-up process is called titration, and it works the same way with semaglutide and tirzepatide.
Side effects
The most common side effects in the trials were nausea, diarrhea, constipation, vomiting, and lower appetite. They were most common while the dose was going up. Higher doses led more people to stop the medication because of side effects. Trials also saw a small rise in resting heart rate, which matters to us because we look at every plan through a heart health lens.
Why we caution against online "research" retatrutide
Because retatrutide is not approved, some websites sell it as a "research chemical" labeled not for human use. Those products are not checked for purity, sterility, or the right dose. You cannot know what is actually in the vial. We do not recommend them.
What you can do now
Semaglutide and tirzepatide are FDA-approved for weight management, and tirzepatide produces weight loss in a similar range to the middle retatrutide doses. At Elive Health, we start with labs, look at insulin, blood sugar, thyroid, lipids, and blood pressure, and build a plan that protects muscle while you lose fat. Health Program members save 20% on weight loss medication.
See our medical weight loss options or book a consultation. We see patients in New Braunfels and virtually across Texas.
Retatrutide dosage FAQs
What is the starting dose of retatrutide?
In clinical trials, most people started at 2 mg once weekly before stepping up. Because retatrutide is not approved, there is no official starting dose yet.
What is the highest dose of retatrutide?
The highest dose studied in the main trials was 12 mg once weekly.
How often is retatrutide taken?
Once a week, as an injection under the skin.
Is retatrutide stronger than tirzepatide?
In separate trials, the higher retatrutide doses produced somewhat more average weight loss than tirzepatide. The two have not been compared head to head in a large trial. See Retatrutide vs Tirzepatide for more.
When will retatrutide be available?
Lilly plans to file with the FDA in early 2027. FDA review usually takes many months after that, so approval timing is not known yet.
This article is for education only and is not medical advice. Retatrutide is not FDA-approved. Talk with your own provider before starting any weight loss medication.