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Home/Guides & Tips/Weight loss/

Retatrutide and bodybuilding

Retatrutide and bodybuilding: Can it help build muscle?

There’s talk on bodybuilding forums that weight loss injection retatrutide can help you build muscle. But what’s the truth?

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Medically reviewed by

Dr Earim Chaudry (MBBS), Chief Medical Officer

iconPublished 5th November 2025
Research-Based Guide
Table of contents
  • Can you build muscle while on ...
  • How might retatrutide influenc...
  • Retatrutide bodybuilding dosag...
  • How long does retatrutide take...
  • Bodybuilding on retatrutide: t...
  • Your weight loss journey

It’s not approved yet in the UK, but people are already talking about retatrutide on social media. Some are saying on social media sites like Reddit that it’s ideal for bodybuilding, because it helps burn fat while preserving muscle.

Can you build muscle while on retatrutide?

Yes, you can. Retatrutide doesn’t block or inhibit muscle building at all. But it won’t magically do the work for you.

If you want to build muscle while on retatrutide, you’ll need to do it the old-fashioned way: regular strength training and eating a nutritious diet (including enough protein).

How might retatrutide influence fat vs muscle?

Online, people are claiming that retatrutide can help you shed fat without losing any muscle.

That isn’t completely true. In a phase 2 clinical trial, people with type 2 diabetes lost more fat on retatrutide than dulaglutide and placebo. Though the proportion of muscle mass lost was similar to that on other weight loss treatments.

This suggests that retatrutide is able to preserve the same amount of muscle as existing treatments while leading to a greater drop in weight. So, it might be slightly better at burning fat, but there’s still some loss of muscle.

Retatrutide bodybuilding dosage

To be clear: retatrutide isn’t approved in the UK yet, so it can’t be prescribed or used outside clinical trials.

If you’re wondering about using retatrutide for bodybuilding, it isn’t for that. After approval, it will likely be licensed for medical weight loss in people who are overweight or have obesity, because that is what it has been studied for, not muscle gain. There’s no such thing as a “retatrutide bodybuilding dosage”.

Heads up: retatrutide appears to be available on the so-called “grey market”, which is when you buy products through unofficial channels. Don’t do this: this market isn’t regulated and there’s no guarantee that the products you buy are safe—nor that they are what they say they are. It’s not worth the risk. 

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How long does retatrutide take to kick in?

There isn’t loads of research on retatrutide. But the data we have so far suggests that you could notice changes within a month.

In clinical research, the average loss is around 2-5% body weight after four weeks, depending on the dose. And at 48 weeks, that figure is 24.2% (for the highest dose).

How does that compare to what’s currently on the market? To give an example: the average loss on Wegovy 7.2mg weight loss injections is 18% after 48 weeks (estimated from 72-week data).

Good to know: in clinical studies, the starting retatrutide dose was low and increased every four weeks—just like with other weight loss medicines.

Bodybuilding on retatrutide: tips if you want to keep muscle

Again, you shouldn’t use retatrutide for bodybuilding.

But when losing weight, some degree of muscle loss is to be expected. However, there’s ways you can prevent this:

  • Eat enough protein. High protein intake helps preserve lean body and muscle mass during weight loss. Go for about 1.2–1.6 g/kg/day, distributed across 3–4 eating occasions
  • Hit the gym. Strength training helps to build muscle and improve strength. Aim for at least 2-3 sessions per week

Even if you don’t want a bodybuilder’s physique, it’s super important to maintain your muscles. They keep you fit and healthy: regulating your metabolism, supporting heart health, helping you move, and more.

Your weight loss journey

Interested in weight loss medications? Through Voy’s weight loss programme, you can access licensed options like orlistat capsules, Wegovy and Mounjaro. Your clinician will help you choose what fits your health, goals and preferences.

And in terms of Voy weight loss results: 94% of our patients think it’s the best weight loss programme they’ve tried.

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FAQ

Retatrutide and bodybuilding: FAQ

Dr Earim Chaudry, MBBS
DisclaimerAt Voy, we ensure that everything you read in our blog is medically reviewed and approved. However, the information provided is not meant to replace professional medical advice, diagnosis, or treatment. It should not be relied upon for specific medical advice.
References
icon¹

Cava, Edda, et al. “Preserving Healthy Muscle During Weight Loss,” Advances in Nutritionscribble-underline, vol. 8, issue 3, 2017:511-519 https://pmc.ncbi.nlm.nih.gov/articles/PMC5421125/

icon²

Coskun, Tamer, et al. “Effects of Retatrutide on Body Composition in People with Type 2 Diabetes: a Substudy of a Phase 2, Double-blind, Parallel-group, Placebo-controlled, Randomised Trial,” The Lancet - Diabetes and Endocrinologyscribble-underline, vol. 13, issue 8, 2025:674-684 https://www.thelancet.com/journals/landia/article/PIIS2213-8587(25)00092-0/abstract

icon³

Garvey, W. Timothy, et al. “Triple Receptor Agonist Retatrutide: A Potential Breakthrough in Obesity Pharmacotherapy.” American Journal of Lifestyle Medicinescribble-underline, vol. 19, no. 1, 2025, pp. 12–20. https://journals.sagepub.com/doi/10.1177/15598276251344827.

icon⁴

Jastreboff, Ania M., et al. “Triple-hormone-receptor Agonist Retatrutide for Obesity—a Phase 2 Trial.” The New England Journal of Medicinescribble-underline, vol. 389, no. 6, 2023:514-526 https://www.nejm.org/doi/full/10.1056/NEJMoa2301972

icon⁵

Wilding, John P.H., et al. “Once-weekly Semaglutide in Adults with Overweight or Obesity.” The New England Journal of Medicinescribble-underline, vol. 384, no. 11, 2021:989-1002 https://www.nejm.org/doi/full/10.1056/NEJMoa2032183

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