Retatrutide: what it is, what it's for and why everyone is talking about it

What exactly retatrutide is

Retatrutide (research name LY3437943) is an injectable medicine that Eli Lilly is developing to treat obesity and type 2 diabetes. It belongs to the same family as Ozempic, Wegovy or Mounjaro — the so-called gut hormone analogues — but goes a step further in its mechanism.

While semaglutide (Ozempic, Wegovy) acts on a single hormone and tirzepatide (Mounjaro) on two, retatrutide acts on three at once. That's why it's known as a 'triple agonist' and why it generates so much excitement: in preliminary studies it has shown the largest weight losses seen so far with a medicine.

How the triple mechanism works

Retatrutide mimics three hormones your body produces naturally that regulate hunger, glucose and energy expenditure:

• GLP‑1: reduces appetite and slows stomach emptying, so you feel full sooner and for longer.
• GIP: improves how the body manages glucose and boosts the effect of GLP‑1 on appetite.
• Glucagon: increases energy expenditure, that is, it helps 'burn' more energy at rest.

That combination of eating less and spending more at the same time is what explains such striking results. It's also what sets it apart from current GLP‑1s, which mainly work by reducing appetite.

What results it has shown in trials

In the phase 2 trial published in The New England Journal of Medicine, people who received the highest dose lost on average around 24% of their body weight in 48 weeks, a figure higher than any other obesity medicine available today. Even so, it's worth being cautious: these are results from studies still under way and the phase 3 trials — the ones that confirm long-term efficacy and safety — are still to come.

The retatrutide data are promising, but 'promising' doesn't mean 'available'. An experimental medicine isn't a treatment option yet.

Known side effects

Like the rest of the medicines in this family, the most common adverse effects in the studies were digestive and mild to moderate in intensity, especially when increasing the dose:

• Nausea, especially at the start of treatment.
• Diarrhoea or constipation.
• Vomiting and abdominal discomfort.
• Reduced appetite (the intended effect, but sometimes excessive).

As an experimental medicine, its full safety profile is still being studied. That's why no serious professional can recommend it to you today outside a clinical trial.

So what can you do today?

If retatrutide interests you because you want to lose weight effectively, the good news is that you don't have to wait years. Approved, legal treatments with years of evidence behind them already exist: semaglutide and tirzepatide, prescribed with a prescription and medical follow-up.

At DoctorLife, a free medical assessment lets you find out whether one of these treatments fits your case, without resorting to experimental medicines or illegal online purchases.

Frequently asked questions