1d • General discussion
Reta
Retatrutide is an investigational once-weekly injectable medication being developed by Eli Lilly for obesity, type 2 diabetes, and related metabolic diseases. It is not yet FDA-approved and is currently in late-stage (Phase 3) clinical development.
What makes it different?
Current weight-loss medications target one or two hormone pathways:
- Semaglutide (Ozempic/Wegovy): GLP-1 receptor agonist
- Tirzepatide (Mounjaro/Zepbound): GLP-1 + GIP receptor agonist
- Retatrutide: GLP-1 + GIP + glucagon receptor agonist (a “triple agonist”)
The three hormones work together in complementary ways:
- GLP-1: Reduces appetite, slows stomach emptying, improves blood sugar.
- GIP: Enhances insulin release and appears to boost weight-loss effects when combined with GLP-1.
- Glucagon: Increases energy expenditure (burning more calories) and may help mobilize fat stores, although it can also raise blood sugar if used alone. In retatrutide, the GLP-1 and GIP effects help offset that.
How effective is it?
Retatrutide has produced some of the largest weight-loss results seen with any medication:
- In Phase 2 studies, people lost up to about 24% of their body weight after 48 weeks.
- More recent Phase 3 trials reported around 28% average weight loss at the highest dose over 80 weeks in adults with obesity without diabetes.
For people with type 2 diabetes, weight loss has been somewhat lower (which is common with obesity medications), around 20–21%, while also substantially improving blood sugar control.
Side effects
The side effects look similar to other GLP-1 medications:
- Nausea
- Vomiting
- Diarrhea
- Constipation
- Reduced appetite
These are usually most noticeable while increasing the dose. Researchers are still studying long-term safety because the glucagon component is relatively new compared with existing GLP-1 drugs.
Is it available?
No. As of August 2026:
- Retatrutide is not FDA-approved.
- Lilly has reported positive Phase 3 results and plans to seek FDA approval, but it is currently available only through clinical trials. Health experts advise avoiding products sold online claiming to be retatrutide because they are unapproved and may be unsafe.
How does it compare with tirzepatide?
While direct head-to-head trials are limited, the available evidence suggests:
Feature
Tirzepatide
Retatrutide
Targets
GLP-1 + GIP
GLP-1 + GIP + glucagon
Weekly injection
Yes
Yes
Average weight loss in major trials
~20–23%
Up to ~28%
Blood sugar improvement
Excellent
Excellent
Approval status
Approved
Investigational
The extra glucagon activity may explain why retatrutide appears capable of even greater weight loss, but definitive comparisons will require direct clinical trials and longer-term safety data.
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