What is retatrutide used for?

Indications that have reported

Two Phase 3 readouts have landed. TRIUMPH-4, reported in December 2025, enrolled adults with obesity and knee osteoarthritis and recorded average weight loss of 28.7% at the 12 mg dose across 68 weeks; the same study recorded a 44-point improvement on the WOMAC pain subscale, an osteoarthritis measure. TRANSCEND-T2D-1, reported in March 2026, enrolled people with type 2 diabetes and recorded a 2.0% reduction in A1C alongside 16.8% weight loss at 12 mg over 40 weeks.

Those two figures answer different questions and are not interchangeable. A1C measures glycaemic control; the weight figures measure body mass. A study reporting both is reporting two outcomes, not one outcome twice.

Indications still under investigation

• Cardiovascular outcomes — TRIUMPH-3 is running in patients with established cardiovascular disease, with results expected in 2027 or later.
• Obstructive sleep apnea — Phase 2 recorded a 42% reduction in the apnea-hypopnea index; a dedicated Phase 3 sits in the TRIUMPH programme.
• Metabolic liver disease (MASH) — Phase 2 recorded reductions in liver fat and improved insulin sensitivity, with a Phase 3 underway.

A Phase 2 signal is a reason to run a Phase 3, not a smaller version of one. The apnea and liver figures above are the former, and the distinction is the whole difference between an indication that has been demonstrated and one that is being tested.

Why the list is broader than most compounds’

Retatrutide agonises three receptors — GLP-1, GIP and glucagon — where semaglutide engages one and tirzepatide two. The glucagon arm is what makes a wide indication list mechanistically plausible, because glucagon signalling touches hepatic fat and energy expenditure rather than appetite alone. Plausible is not demonstrated: the breadth of the programme reflects a hypothesis Lilly is funding, and each indication stands or falls on its own readout.

That is also why this page will date. Two of six indications have reported; the rest are scheduled through 2027, and any of them can fail.

• No approval anywhere — every use below is investigational.
• Reported: obesity (TRIUMPH-4, 28.7% at 12 mg / 68 weeks) and type 2 diabetes (TRANSCEND-T2D-1, 2.0% A1C at 12 mg / 40 weeks).
• Reported alongside obesity: knee osteoarthritis pain (44-point WOMAC improvement, TRIUMPH-4).
• Running, not reported: cardiovascular outcomes, sleep apnea, metabolic liver disease.