Retatrutide: New triple agonist GLP-1

Retatrutide clinical trial results

The TRIUMPH-1 trial results were first announced in May 2026 and published in full in the New England Journal of Medicine in September 2026. They showed that retatrutide could help patients lose around a quarter of their body weight, and close to a third for some patients who continued treatment for longer.

The study included 2,339 adults with obesity or overweight who did not have type 2 diabetes. They were treated for 80 weeks.

The published paper's main analysis counts everyone who started the trial, including people who stopped treatment early. The table also shows Eli Lilly's figures for people who stayed on treatment as intended, which is the effect you'd expect if you keep taking it.

Other health benefits measured during retatrutide trials

The trial also measured other health benefits. People with knee osteoarthritis reported less knee pain. People with obstructive sleep apnoea had substantially fewer breathing interruptions per hour while asleep, around 32–34 fewer on the 9 mg and 12 mg doses compared with about 10 fewer on placebo.

Most common side effects reported during trials

The most common side effects were gastrointestinal: nausea, diarrhoea, constipation and vomiting. These were mostly mild to moderate and resolved during treatment. Around 11% of people on the 12 mg dose stopped treatment because of side effects, compared with about 5% on placebo.

Retatrutide dosage and administration

Like other weight management medications in its class, Retatrutide is designed as an injectable treatment. It is administered once weekly via a subcutaneous injection. This means it goes just under the skin rather than into a muscle or vein.

If approved, it will likely come in a pre-filled pen device, similar to devices used for Mounjaro and Wegovy. As with other weight loss injections, consistency will be important, so taking it on the same day each week helps maintain steady levels of the drug in your system.

Each clinical trial showed patients starting at different doses. Phase 2 trials started at 1mg where as Phase 3 trials started at 2mg.

There isn't an official confirmation of Retatrutide strengths or dosing schedule yet, as it's still being studied. However, like other weight loss injections, it was given at a low starting dose in trials and increased gradually over several weeks. This step-by-step approach allows the body to adjust to the medication and helps reduce the chance of side effects

Retrutide starting and titration schedule

To give your body time to adjust, treatment does not start at the maximum dose. You will likely begin on a low starting dose of 4mg.

If you tolerate the medication well, your clinician will gradually increase the dosage every four weeks. This step-by-step approach, known as titration, is crucial for minimising side effects while slowly building up to the therapeutic maintenance dose where maximum weight loss occurs.

Always follow your prescriber's instructions.

Any dose schedule shown here is a general guide. Your own dose, and how quickly it increases, will be set by your prescriber based on your individual response and tolerability.