Here are some of the questions that come up most often about retatrutide. We’ve tried to answer them based on what’s actually known from the clinical trials so far.
What exactly is retatrutide? Retatrutide is an investigational medication being developed by Eli Lilly. It’s a once-weekly injection that works on three hormone receptors at the same time — GLP-1, GIP, and glucagon. Because it hits three targets instead of one or two like current medicines, researchers think it could produce stronger effects on weight and metabolism.
How much weight loss has been seen in the trials? In the Phase 3 TRIUMPH-1 trial results released in May 2026, people taking the highest dose (12 mg) lost an average of about 28.3% of their body weight over 80 weeks. That’s roughly 70 pounds for someone starting around 250 pounds. A good portion of participants lost 30% or more. These are some of the highest numbers seen so far in obesity trials, but individual results still vary quite a bit.
When will retatrutide be available? As of June 2026, it is still not approved anywhere. Eli Lilly is running several Phase 3 trials, and the company has said they expect to file for approval sometime in 2027, with possible availability in late 2027 or 2028 if everything goes smoothly. These timelines can shift.
What are the most common side effects? The side effects that show up most often are similar to other GLP-1 medicines: nausea, diarrhea, vomiting, and constipation. These tend to be worse when people first start or when the dose is increased, and they often get better over time. One side effect that appears more noticeable with retatrutide is dysesthesia — a tingling or unusual skin sensation. Most cases have been mild.
How is retatrutide dosed in the studies? In the main trials, treatment starts at 2 mg once a week. The dose is then increased every four weeks, moving up to 4 mg, then 9 mg, and finally 12 mg for those who tolerate it. The slow increase is done on purpose to help reduce stomach-related side effects.
Is retatrutide better than Mounjaro or Wegovy? In the head-to-head data we have so far, retatrutide has shown higher average weight loss than tirzepatide (Mounjaro/Zepbound) and semaglutide (Wegovy/Ozempic). However, these are still early comparisons from separate trials. Direct head-to-head studies are ongoing, and we’ll know more once those results come out. “Better” also depends on side effects, how well someone tolerates the medicine, and other health factors.
Can I buy retatrutide right now? No. It is not approved for sale or prescription anywhere. Some websites claim to sell it for “research purposes,” but those products are not the same as what’s being tested in clinical trials, and using them carries real risks. We strongly recommend waiting for proper regulatory approval and medical supervision.
Are there ongoing clinical trials I could join? Yes, several TRIUMPH trials are still running or have recently completed enrollment. The best place to check is ClinicalTrials.gov. Search for “retatrutide” or “LY3437943” and filter by location and status. Keep in mind that trial spots are limited and have specific eligibility rules.
Does retatrutide help with anything besides weight loss? Early data suggests it may also reduce liver fat and improve certain heart and metabolic markers. Some trials are specifically looking at people with osteoarthritis of the knee and sleep apnea. These are still being studied, so we don’t have final answers yet.
Who might benefit most from retatrutide once it’s approved? Based on current trial data, it seems most relevant for adults with obesity or overweight plus at least one weight-related health condition. As with any medication, the decision should be made together with a doctor after looking at your full health picture, other medications, and personal goals.
We’ll keep adding to this page as new trial results come out and more questions surface.