What are the side effects of Mounjaro, and does it cause muscle loss?
The common side effects and when they ease, what UAE doctors are warning about muscle, what the body-scan studies show, protein and strength training, and the serious risks.
Written for the United Arab Emirates. Other country versions are coming.
Stomach effects are the most common. In the weight trial, about 25 to 33 in 100 people on Mounjaro felt sick, against about 10 in 100 on a dummy injection, mostly while the dose rose. UAE doctors warn that some weight lost is muscle. In the trial, about a quarter of it was lean mass, which includes muscle.
Key takeaways
- In the EU label’s weight trial, nausea hit about 25 to 33 in 100 people on Mounjaro (24.6% to 33.3%, by dose), against about 10 in 100 on a dummy injection, and was worst while the dose rose.1
- Hair loss is listed as common on the EU Mounjaro label (between 1 in 100 and 1 in 10 people), mainly in people treated for weight.1
- UAE doctors interviewed by Khaleej Times in September 2025 cautioned that "much of the loss may be muscle rather than fat" without the right habits.2
- In a body-scan study within SURMOUNT-1, about 75% of the weight lost on Mounjaro was fat and 25% was lean mass, the same split as on the dummy injection.3
- A US nutrition advisory says 1.2 to 1.6 g of protein per kg a day has been proposed during weight loss, alongside strength training.4
On this page
What are the most common side effects of Mounjaro?
Stomach and gut effects: nausea, diarrhoea, vomiting, constipation and stomach pain. In the weight trial, 55.6% to 60.8% of people on Mounjaro had one, against 30.3% on a dummy injection.1
- GLP‑1 medicines are prescription-only in the UAE. They should only be used under medical supervision, with a prescription from a doctor licensed in the UAE.5
- Label facts here come from the EU label (EMA), the UK label or the US label (FDA), named each time. We could not find the UAE pack leaflets online, so check the leaflet in your own pack.
- Every risk of these medicines is in Guide 5: Side effects and risks.
- This post describes labels, rules and trials. It is not a plan for your treatment, and no dose or brand guarantees any result.
| Side effect | Mounjaro 5 / 10 / 15 mg | Dummy injection |
|---|---|---|
| Any stomach or gut effect | 55.6% / 60.8% / 59.2% | 30.3% |
| Nausea | 24.6% / 33.3% / 31.0% | 9.5% |
| Diarrhoea | 18.7% / 21.2% / 23.0% | 7.3% |
| Stopped because of stomach effects | 1.9% / 4.4% / 4.1% | 0.5% |
Weight-management trial in people without diabetes, EU Mounjaro label section 4.8, checked 12 Oct 2026.1
Most of these effects were mild (60.8%) or moderate (34.6%).1 Other common effects on the EU label include indigestion, burping, reflux, tiredness, dizziness, hair loss and reactions where you inject.1
Our post on Mounjaro vs Ozempic vs Wegovy compares side effects across the medicines.
Do the side effects go away?
For most people they ease. The EU label says nausea, vomiting and diarrhoea were more common while the dose was going up, and fell over time.1
Mounjaro starts at 2.5 mg and rises in steps of at least 4 weeks.1 A US advisory suggests small, regular meals and enough fluids, and notes that vomiting is more likely after large meals.4
Does Mounjaro cause muscle loss?
Some of the weight lost is muscle, as with any big weight loss. In SURMOUNT-1’s body-scan study, about a quarter of the weight lost on Mounjaro was lean mass.3
In Khaleej Times in September 2025, UAE doctors cautioned that “much of the loss may be muscle rather than fat”.2 One clinic’s medical director said some patients lose weight on the scale that is “mostly muscle”.2 A telehealth company founder quoted in the same report put it at about 40%, for people who skip strength training and protein.2
The trial measurements are lower than 40%. Of 160 people scanned during SURMOUNT-1, the 124 on Mounjaro lost 21.3% of their weight, 33.9% of their fat and 10.9% of their lean mass. About 75% of what was lost was fat, the same split as on the dummy injection with diet and activity advice.3
Lean mass is not all muscle: it includes water and organs. The 2025 advisory estimates muscle is about half of it.4 By our arithmetic, that is roughly 1 kg of muscle in every 8 kg lost on Mounjaro. Across the whole SURMOUNT-1 trial, people on Mounjaro also reported better physical function than those on the dummy injection.3
How much protein should you eat on Mounjaro?
There is no fixed target. A US nutrition advisory says 1.2 to 1.6 g per kg of body weight a day has been proposed during active weight loss, above the usual 0.8 g.4
For a 70 kg person, 1.2 to 1.6 g/kg is about 84 to 112 g a day. The advisory warns that using your actual weight can overestimate the need if you carry a lot of fat, and offers a simpler 80 to 120 g a day as an alternative.4
Guide 5: every common and serious side effect, when to get help, and how to report one in the UAE.
What exercise protects muscle?
Strength training. The advisory says strength or mixed training is “well established” to help keep lean mass; aerobic exercise alone has a smaller effect.4
Abu Dhabi’s obesity standard asks doctors to present medicine as an add-on to better diet and more activity, “including resistance exercises”.6 Resistance means working against weight: dumbbells, bands, machines or your own body weight.
How much. The advisory suggests strength training at least 3 times a week, plus at least 150 minutes of moderate aerobic activity a week.4 If you have kidney disease, ask your doctor before raising your protein.
The same standard notes that the UAE’s outdoor heat limits activity, so plan indoor options for summer.6 Our guide Life on a GLP‑1 has an example week.
Which side effects are serious?
Pancreatitis, gallbladder problems, dehydration that harms the kidneys, and low blood sugar if you also take insulin or a sulphonylurea. Most are uncommon.1
- Pancreatitis is uncommon (1 in 100 to 1 in 1,000). The sign is severe stomach pain that won’t go away, sometimes spreading to the back.1
- Gallbladder: in the weight trials, acute gallbladder disease affected about 20 in 1,000 people on Mounjaro, against 16 in 1,000 on a dummy injection.1
- Dehydration from vomiting or diarrhoea can lead to kidney failure, the EU label warns.1
- Low blood sugar (clinically significant or severe) hit 10 to 14 in 100 people with diabetes when Mounjaro was added to a sulphonylurea, and 14 to 19 in 100 with basal insulin.1
- Surgery or sedation: food can stay in the stomach longer, and cases of breathing in stomach contents under anaesthesia have been reported. The label says this risk should be considered beforehand.1
Questions people ask
How common is nausea on Mounjaro?
In the EU label’s weight trial, about 25 to 33 in 100 people on Mounjaro felt sick, against about 10 in 100 on a dummy injection. It was worse while the dose went up.1
Does Mounjaro make your hair fall out?
Hair loss is listed as common on the EU label, between 1 in 100 and 1 in 10 people, mainly in people treated for weight.1
How much of the weight lost on Mounjaro is muscle?
In a SURMOUNT-1 body-scan study, about 25% of weight lost was lean mass, which includes muscle, water and organs. About 75% was fat.3
How much protein should I eat on Mounjaro?
A US advisory says 1.2 to 1.6 g per kg a day has been proposed during weight loss, or a simpler 80 to 120 g a day.4
How do I report a side effect in the UAE?
Tell your doctor or pharmacist. In Abu Dhabi, the DoH takes reports at [email protected].5
Shorter answers: How do I report a side effect in the UAE?
How we researched this
On 12 Oct 2026 we read the EU Mounjaro label (section 4.8 and the weight trials) and a Khaleej Times report quoting UAE doctors (September 2025). The SURMOUNT-1 body-scan study and the 2025 US nutrition advisory were already checked for our other GLP Guidebook pages.
The 40% muscle figure in the news report came from a telehealth company founder, not from a study; we show it next to the trial data. We name no clinic or telehealth company. Lilly, which makes Mounjaro, funded SURMOUNT-1 and its body-scan study.
Before you move on
- Nausea and gut effects are common, and mostly ease after dose steps.
- About a quarter of weight lost in the trial was lean mass.
- Protein first at meals; strength training a few times a week.
- Severe stomach pain that won’t stop: call 998.
More from the UAE blog
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An independent guide to GLP‑1 medicines. We don't sell medicines, take drug-company money or earn clinic commissions. Once a month: UAE approvals, official price changes, insurance rules and safety alerts. How we write
Sources
- European Medicines Agency. Mounjaro (tirzepatide): EU summary of product characteristics and package leaflet (EU label), sections 4.1, 4.2, 4.4, 4.8, 5.1, 6.3, 6.4. PDF ema.europa.eu
- Khaleej Times. UAE doctors warn of health risks as residents turn to new weight loss drugs. 19 September 2025. khaleejtimes.com
- Look M et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study. Diabetes Obes Metab 2025. Funded by Eli Lilly. doi:10.1111/dom.16275 doi.org
- Mozaffarian D et al. Nutritional priorities to support GLP‑1 therapy for obesity: a joint advisory (ACLM, ASN, OMA, The Obesity Society). Obesity 2025;33:1475–1503. Some authors declare Novo Nordisk or Eli Lilly roles. doi:10.1002/oby.24336 doi.org
- Department of Health – Abu Dhabi. Circular 48/2026, 16 March 2026: alert on fake GLP‑1 products. GLP‑1 medicines "are prescription-only medicines and should only be used under medical supervision"; unregistered products are sold online and on social media; reports to the DoH pharmacovigilance team at [email protected]. Summarised, not reproduced, as the circular asks. PDF doh.gov.ae
- Department of Health – Abu Dhabi. Standard for Non-Surgical Management of Obesity, DOH/ST/HPS/Non-Surgical-MO/V1/2025, published February 2025. Sections 3.3–3.4, 4.1 and Appendix 4. PDF doh.gov.ae
- Department of Digital Ajman. Handling emergencies: 999 police, 998 ambulance, 997 civil defence; Ministry of Health and Prevention hotline 80011111 for fake or harmful medicines. Checked 12 October 2026. ajman.ae
Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error
How this post was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor or pharmacist before starting, stopping or changing any medicine. How we write