Retatrutide common uses, half-life, side effects and more

Retatrutide is a synthetic peptide in development as a once-weekly injection for obesity and related metabolic conditions. It activates three metabolic hormone receptors at once. Those receptors are GIP, GLP-1, and glucagon. Adding the glucagon target is what sets it apart from the dual-receptor obesity drugs already approved. It is investigational and not approved by any health authority in any country. There is no legitimate prescription supply. People who obtain it use unapproved research-grade material of unverified purity.

• Weight loss and obesity
• Type 2 diabetes glycemic control
• Liver fat reduction in fatty liver disease (MASLD)
• Obstructive sleep apnea in people with obesity
• Knee osteoarthritis pain alongside weight loss
• Community off-label use for body-composition change

Once weekly

Once-weekly subcutaneous injection. Phase 2 tested 1 mg, 4 mg, 8 mg, and 12 mg. The phase 3 program starts at 2 mg and steps up every 4 weeks. It reaches the top 12 mg dose by about week 17. Maintenance targets are 4 mg, 9 mg, or 12 mg. Community users generally mirror the trial titration and settle on a weekly maintenance dose between about 4 mg and 12 mg. Many start lower and step up more slowly than the trials did.

About 6 days (144 hours) in humans. This supports once-weekly subcutaneous dosing.

• Nausea (very common, dose-dependent, and worst during dose escalation)
• Vomiting and diarrhea (common and dose-dependent)
• Constipation (common)
• Injection-site reactions (usually mild and more frequent at higher doses)
• Dysesthesia (skin tingling, burning, or numbness) that was mostly mild and usually eased during treatment
• Resting heart rate rise of about 7 bpm that peaks near week 24 and eases afterward
• Pancreatitis (uncommon but serious)
• Gallbladder problems or gallstones (uncommon and linked to rapid weight loss)

Retatrutide activates the GIP, GLP-1, and glucagon receptors. Its strength at each is very different. It is most potent at the GIP receptor. There it is roughly 8.9 times as active as the body's own GIP. It is weaker than the natural hormones at the other two receptors. It runs about 0.4 times as active at GLP-1 and 0.3 times at glucagon. GLP-1 and GIP signaling raises glucose-dependent insulin release and reduces appetite. GLP-1 also slows gastric emptying. The glucagon signal adds energy expenditure and fat breakdown. That glucagon component is the leading explanation for its greater weight loss compared with the dual GIP and GLP-1 drugs. No trial has yet isolated it. The molecule is a 39-amino-acid peptide carrying a C20 fatty diacid chain that binds albumin and extends how long it stays active.

Human evidence is recent and still short in duration. The phase 2 obesity trial reported a mean 24.2% weight loss at 48 weeks on 12 mg (NEJM 2023). A phase 2 type 2 diabetes trial and a phase 2a liver-fat sub-study followed. The phase 3 TRIUMPH program is underway. TRIUMPH-4 enrolled adults with obesity and knee osteoarthritis. Its December 2025 readout reported a mean 28.7% weight loss at 68 weeks on 12 mg. It also reported a statistically significant reduction in knee osteoarthritis pain. Further phase 3 readouts through 2026 cover obesity, type 2 diabetes, obstructive sleep apnea, cardiovascular and renal outcomes, liver disease, and chronic low back pain. The longest published data runs 68 weeks. That is shorter than the multi-year evidence behind semaglutide and tirzepatide. No cardiovascular-outcomes trial has finished. No pregnancy-exposure data exists yet.

• Gray-market retatrutide is unapproved and can vary in purity, dose accuracy, and sterility
• The GLP-1 class carries a presumed thyroid C-cell tumor signal that makes it inadvisable with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2
• Acute pancreatitis is a rare but serious risk across the GLP-1 class
• Dysesthesia is a phase 3 signal of tingling, burning, or numbness of the skin that reached about 21% at the 12 mg dose and was mostly mild
• Resting heart rate rises by roughly 7 bpm at the highest dose while the long-term cardiovascular risk stays unknown until outcomes trials finish
• Retatrutide is not for use in pregnancy, breastfeeding, type 1 diabetes, or a history of pancreatitis
• Rapid weight loss above 20% of body weight in a year makes muscle loss a real risk without resistance training and enough protein
• Oral hormonal birth control may become less reliable during use as it does with tirzepatide so a non-oral or barrier method is safer