Retatrutide: what we know and what you can do while you wait

What is retatrutide, and how does it differ from current GLP-1 medicines?

Retatrutide is a medicine in development by Eli Lilly, given as a weekly injection. It is a triple agonist: it activates receptors for three hormones at once—GIP, GLP-1 and glucagon—which are involved in appetite and energy expenditure [2]. Medicines already authorised in Spain, such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro), act on one or two of these pathways; retatrutide adds the third.

It is not an improved version of a medicine you may already be taking, and it does not replace an assessment by the person who prescribes your treatment. The main guide to GLP-1 medicines explains where each molecule fits, including orforglipron and CagriSema, two other medicines in this family that are also not available in Spain.

What stage has development reached?

A completed Phase 3 trial and a planned application are not an authorisation. The US medicines regulator, the FDA, may request more data, approve the medicine subject to conditions, or reject the application. It would then need a separate European assessment, followed later by marketing in Spain. Any arrival date you see today is an estimate, not an official timetable.

An average trial result can help put a future option into context; it does not replace your doctor’s assessment or the eating plan you need today.

What did the TRIUMPH-1 trial find?

TRIUMPH-1 included 2,339 adults with obesity, or with overweight and a weight-related condition [1]. At 80 weeks, average weight loss was 19.0%, 25.9% and 28.3% with the 4, 9 and 12 mg doses [1]. It was 2.2% with placebo [1]. In an extension to 104 weeks, participants with a body mass index (BMI) of 35 or higher who continued on 12 mg reached 30.3% [1].

The most common side effects affected the digestive system: nausea, diarrhoea, constipation and vomiting [1]. At 12 mg, 11.3% stopped treatment because of adverse effects, compared with 4.9% on placebo [1]. Dysesthesia, an unusual skin sensation, was also reported in 12.5%, compared with 0.9% [1].

This is the average result from a trial with its own population and methods. It does not compare retatrutide with semaglutide, tirzepatide or CagriSema, which were studied in trials with different designs.

What you can focus on while you wait

If you are already taking semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro) or liraglutide (Saxenda), the priority is to make sure your meals remain adequate even if your appetite has decreased. Include a source of protein, vegetables and a carbohydrate food at each main meal. Our weekly meal plan for eating while taking a GLP-1 offers meal and portion ideas.

Protein and strength matter even more with greater weight loss

The greater the weight loss, the more muscle mass you may lose with it if you do not take steps to prevent this. A joint advisory from four US scientific societies recommends paying attention to protein and strength exercise to protect physical function during treatment [4]. This becomes even more important with medicines that lead to greater weight loss.

Our guide to protein and muscle with GLP-1 medicines explains how to spread your protein intake through the day and get started with strength exercise at your own level.

If you are not taking a GLP-1 medicine yet

The decision to start treatment always belongs with your doctor. While this is being considered, our nutrition support for people taking GLP-1 medicines service can help you review your meals, activity and relevant health history to inform your plan. You can start organising your meals, rest and movement now, without waiting for a new medicine.

If you have had an eating disorder, discuss it with your doctor and a mental health professional before starting or changing any weight treatment. Our guide to GLP-1 medicines and eating disorders explains what to look out for.

What we see in consultations

This is one of the questions that comes up most often in consultations: is it better to wait for a medicine with better results, or start with what is already available? There is no single answer. It depends on your clinical situation, how well you tolerate the available options and how long the wait might be. That decision is for your doctor.

Another common mistake is to read an average trial percentage as if it were your own result. Each person’s starting point, tolerance and follow-up make a difference. If you are following a prescribed treatment, do not change or stop it because of news about another medicine: speak to the person who prescribes it first.

Your first step this week

Check your smallest meal of the day and see whether it includes a source of protein. If not, add a plain yoghurt, an egg or a little fresh cheese.