All about retatrutide: the newest weight-loss medicine

Retatrutide is a new medicine currently being developed by the pharmaceutical company Eli Lilly [1].

Where most weight-loss medicines target one or two hormones, retatrutide tackles three at once: GLP-1, GIP and glucagon [2].

These hormones control processes in your body around hunger, energy expenditure and fat storage. In other words: retatrutide can help you eat less and give your metabolism a boost.

Overweight and the health problems that come with it are increasingly common. Retatrutide may offer a promising new way to lose weight effectively [1].

What makes retatrutide so unique is that it works on three hormones at the same time:

1. GLP-1:Curbs appetite and slows stomach emptying, so you feel full sooner.

2. GIP:Supports insulin production and influences how your body stores fat.

3. Glucagon:Converts stored fat into energy, so your body burns more.

You may recognise this: you try to eat less and move more, but the number on the scales doesn’t change. That’s often because your body starts saving energy as a survival mechanism.

Retatrutide appears to break this mechanism by reducing hunger and increasing fat burning at the same time.‍

How does it differ from other weight-loss medication?

Most existing weight-loss medicines target one or two hormones.

Semaglutide (Ozempic, Wegovy) affects only GLP-1, while tirzepatide (Mounjaro) tackles both GLP-1 and GIP.

Retatrutide goes a step further by also activating the glucagon receptor. This hormone helps your body burn stored fat and use it as energy.

Thanks to this extra action, retatrutide may be more effective against stubborn fat, such as organ fat, and may therefore produce greater weight loss than earlier medicines.

The first clinical studies show impressive results.

In an extensive phase 2 study, published in The New England Journal of Medicine, participants lost on average over 24% of their body weight after 48 weeks [3].

Even more recent data from the phase 3 TRIUMPH-4 trial show that people on the highest dose lost on average 28.7% of their body weight (around 32 kilos) after 68 weeks [4].

The effect on the liver is also striking: in patients with fatty liver disease, harmful fat decreased by more than 80%, and most participants had an almost healthy liver again afterwards [5].

But the benefits of retatrutide go beyond weight loss and organ fat:

• Osteoarthritis and joint pain:the same TRIUMPH-4 study (December 2025) shows that patients with knee osteoarthritis reported a 60% reduction in their pain [4].

• Type 2 diabetes:in March 2026, Eli Lilly published the results of the TRANSCEND-T2D-1 trial. Patients lost on average almost 17% of their body weight in 40 weeks and their blood sugar level (HbA1c) fell by 2.0% [6]. This makes retatrutide particularly interesting for people who have both overweight and diabetes.

Before a medicine like retatrutide is allowed onto the market, it has to go through rigorous clinical trials to prove that it is both effective and safe.

Retatrutide is currently in the final phase 3 trials.

An important part of this is the TRIUMPH-Outcomes study [7]. This large-scale, global study is investigating whether retatrutide, in addition to weight loss, can also help prevent heart and kidney complications in people with overweight.

This information is important for doctors: it shows who benefits most from the treatment and which possible long-term effects and side effects (such as gastrointestinal complaints) may occur.

Because the phase 3 trials are still ongoing, retatrutide has not yet been officially approved by health authorities such as the American FDA or the European EMA.

This means the medicine is not yet available through pharmacies or regular doctors. It is expected that it can only be prescribed at the end of 2026 or in 2027, once the trials have been fully completed and long-term safety has been confirmed.

Beware:unregulated ‘peptides’ are being offered online. The safety, purity and effectiveness of these products are uncertain and may pose health risks.

Thanks to its unique triple action, retatrutide promises to be an important step in weight loss and metabolic health. The first research results are promising.

We’ll need to be patient a little longer. Long-term safety and effects must first be fully confirmed in the final phase 3 trials before retatrutide will be available at the pharmacy.

But you don’t have to wait to reach your target weight. With today’s medical options, you can start your weight-loss journey today.

Curious which personalised treatment plan best suits your body and goals? Fill in the short online questionnaire and find out straight away.

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What are the expected side effects of retatrutide?

As with existing weight-loss medication, such as Ozempic, Wegovy and Mounjaro, the most commonly reported side effects in current studies are gastrointestinal complaints. Think of nausea, diarrhoea, constipation or vomiting. These complaints are usually mild to moderate and occur mainly when the dose is increased. Because the phase 3 trials are still ongoing, the definitive side effects are currently being mapped out in detail.

Is retatrutide a pill or an injection?

In the current clinical trials, retatrutide is administered via a weekly subcutaneous injection. This works similarly to medicines such as Wegovy and Mounjaro. At the moment, no pill version is in development.

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Is retatrutide better than Ozempic or Wegovy?

Although the definitive phase 3 results are still awaited, the preliminary data suggest that retatrutide may be more powerful. Where semaglutide (the active ingredient in Ozempic and Wegovy) targets one hormone (GLP-1), retatrutide affects three (GLP-1, GIP and glucagon). This unique combination appears to produce more weight loss and a faster breakdown of fat reserves.

Will I also lose muscle mass with retatrutide?

With rapid and substantial weight loss, the body can break down muscle mass as well as fat. Muscles are essential for a healthy metabolism. That’s why it’s important during treatment to eat enough protein and do strength training, so that you specifically lose fat and maintain your muscle mass.

What happens if I stop the medication?

As with other chronic treatments, the effect can disappear if you stop without making structural changes to your lifestyle. Think of the medication as the foundation of a house: it brings your biology into balance and supports weight loss. Without lasting changes in diet and exercise, the weight often comes back.

Can I already order retatrutide online?

No. Retatrutide has not yet been approved by health authorities. Websites that supposedly offer ‘retatrutide peptides’ are selling illegal and unregulated products, whose safety and purity are not guaranteed. Using them can pose serious health risks.

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