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Why has my weight loss stopped on Mounjaro or Wegovy?

Why weight loss slows and then levels off, how much people lose first, how a plateau differs from a slow start, and what a prescriber checks. Trial averages, named and dated.

GLP Guidebook teamPublished 14 Oct 20266 min read13 sourcesWritten from published sources
What we checked13 sources, each one opened and linked to the sentence it supportsLast checked 14 Oct 2026 · Next review due 14 Oct 2027 · How we write

Written for the UK.

The short answer

A plateau is expected on Mounjaro (tirzepatide) or Wegovy (semaglutide). In a Lilly analysis of SURMOUNT-1, about 9 in 10 people who stayed on Mounjaro and lost at least 5% had levelled off by week 72. The body pushes back as weight falls. Losing under 5% in 6 months is different: NICE asks for a review.

Key takeaways

  • In a Lilly-funded analysis of SURMOUNT-1, 88 to 90 in 100 people who stayed on Mounjaro and lost at least 5% had reached a weight plateau by week 72.1
  • Half of those people had levelled off by week 24 to 36, later for higher starting BMI and higher doses.1
  • One study found appetite rises by about 100 calories a day for each kilogram lost, more than three times the drop in energy the body uses.3
  • In SURMOUNT-1, average weight fell 16.0% to 22.5% on Mounjaro over 72 weeks, against 2.4% on a dummy injection; 25 to 29 in 100 felt sick, against 9 in 100.4,5
  • In SURMOUNT-4, people switched to a dummy injection after 36 weeks regained 14.8% of their weight over the next year.4
Before you go further
  • GLP‑1 medicines are prescription-only medicines in the UK, never sold over the counter.13
  • Never change your dose, skip doses or stop without talking to your prescriber.
  • Figures here are trial averages. Nothing here promises any result.
  • The risks are in our side effects guide.
On this page
  1. Is a plateau normal on Mounjaro or Wegovy?
  2. Why does weight loss slow down?
  3. How much do people lose before it levels off?
  4. What if weight loss stalls in the first months?
  5. What might a prescriber check?
  6. What happens if you stop at a plateau?
  7. Questions people ask
  8. How we researched this
  9. Sources

Is a plateau normal on Mounjaro or Wegovy?

Yes: in the trials, weight fell fastest in the first months, then slowed and levelled off, even for people who kept taking the medicine.1,2

A 2025 nutrition advisory says weight loss is fastest in the first 6 months, then slows, levelling off at around 18 months.2

A Lilly analysis of SURMOUNT-1 looked at people who kept taking Mounjaro and lost at least 5%. It defined a plateau as weight changing by less than 5% over 12 weeks, and staying that way.1

  • By week 72: 88 to 90 in 100 had reached a plateau.1
  • Half got there by: about 24 weeks if they started overweight, and 36 weeks with a BMI of 35 or more.1
  • Later plateaus: came with higher doses (10 or 15 mg), younger age and being female.1

Why does weight loss slow down?

Because the body pushes back: a lighter body uses less energy, and appetite climbs as weight falls, until intake and use meet again.2,3

In one study, appetite rose by about 100 calories a day for every kilogram lost.3 That was more than three times the fall in energy the body used. It came from a diabetes medicine that is not a GLP‑1, so treat it as a general pattern.3

The 2025 advisory notes these medicines are meant for long-term use, even after a weight goal or plateau is reached. It says weight loss is sustained for at least 4 years when the medicine is continued.2

How much do people lose before it levels off?

In the main trials, average loss over 72 weeks was 16.0% to 22.5% on Mounjaro, depending on dose, and 14.9% over 68 weeks on Wegovy 2.4 mg.4,6

In SURMOUNT-1, 2,539 adults without diabetes took Mounjaro 5, 10 or 15 mg or a dummy injection for 72 weeks.5 Weight fell 16.0%, 21.4% and 22.5%, against 2.4% on the dummy.4 For a 100 kg (15 st 10 lb) person, that is 16 to 23 kg.

Averages hide a range. At least 5% was lost by 89 to 96 in 100 on Mounjaro, against 28 in 100 on the dummy.4 Put the other way, 4 to 11 in 100 on Mounjaro did not reach 5%.

People with type 2 diabetes tend to lose less. NICE says their weight loss may be slower.8 In STEP 2, Wegovy 2.4 mg gave 9.6% in people with diabetes, against 3.4% on a dummy injection.6 STEP 1, a separate trial without diabetes, gave 14.9%.6

What if weight loss stalls in the first months?

That is different from a plateau: NICE and the UK labels call for a review if less than 5% of starting weight is lost after 6 months.4,6,7

For Mounjaro, the 6 months count from reaching the highest dose you tolerate. NICE then says to “decide whether to continue treatment”.7 Wegovy’s UK label asks for the same decision after 6 months on treatment.6

For a person who started at 100 kg, 5% is 5 kg (11 lb). The full rules are in the NICE 5% rule.

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What might a prescriber check?

Your dose and how you take it, missed doses, other health problems and medicines, and the support around eating and activity.4,8

  • The dose. Mounjaro’s recommended maintenance doses are 5, 10 and 15 mg, with rises at least 4 weeks apart.4 See the maintenance dose.
  • Missed doses. The Mounjaro label says take a missed dose within 4 days; after that, skip it.4
  • Regular review. NICE says to monitor the medicine’s effect and reinforce diet and activity advice at regular reviews.8
  • Protein and strength. The 2025 advisory suggests 80 to 120 g of protein a day, or 1.2 to 1.6 g per kg proposed during weight loss.2 It pairs this with strength training at least 3 times a week and 150 minutes of moderate activity.2
  • Kidneys. The advisory says people with or at risk of kidney problems should be monitored. If you have kidney disease, ask your prescriber before raising your protein.2

Our guide to life on a GLP‑1 covers eating and exercise.

What happens if you stop at a plateau?

Weight tends to come back: in SURMOUNT-4, people switched to a dummy injection regained 14.8% over a year, while those who stayed on lost 6.7% more.4

SURMOUNT-4 gave everyone Mounjaro for 36 weeks, then split them at random.4 At week 88, 93 in 100 who stayed on kept at least 80% of the weight they had lost. Of those switched to the dummy, 14 in 100 did.4

The MHRA says to consult a healthcare professional before switching to another GLP‑1.9 Our post on stopping Mounjaro or Wegovy covers weight regain.

RisksThe risks, in brief
  • Stomach effects. In SURMOUNT-1 and -2, 25 to 29 in 100 people on Mounjaro 5 to 15 mg felt sick, against 9 in 100 on a dummy injection. In the main Wegovy 2.4 mg trials pooled on its UK label, 44 in 100 felt sick, against 16 in 100.4,6
  • Gallstones are common (1 in 10 to 1 in 100) on both UK labels.4,6
  • Pancreatitis (an inflamed pancreas) is uncommon (1 in 100 to 1 in 1,000). The MHRA’s warning sign is severe, persistent stomach pain that may spread to the back.4,6,10
  • Higher doses. In the Mounjaro weight trials, 2 in 100 on 5 mg and 4 in 100 on 15 mg stopped because of stomach side effects, against fewer than 1 in 100 on a dummy injection.4
  • Pregnancy. Stop Mounjaro at least 1 month, and Wegovy 2 months, before a planned pregnancy.9
Full detail in our side effects guide →
Get help now: call 999 or go to A&E for severe, persistent stomach pain that may spread to the back. It can be pancreatitis.10 Not sure? Use NHS 111.11 Northern Ireland has no 111: use your GP’s out-of-hours service.12

Questions people ask

Why is Mounjaro not working for me any more?

Weight loss usually slows and levels off. In a Lilly analysis of SURMOUNT-1, about 9 in 10 people who stayed on Mounjaro and lost at least 5% had reached a plateau by week 72.1

How long does a weight-loss plateau last?

In the SURMOUNT-1 analysis, weight stayed broadly steady after levelling off. A 2025 advisory says loss is sustained for at least 4 years when the medicine is continued.1,2

Should I increase my Mounjaro dose if I plateau?

That is your prescriber’s decision. The UK label’s recommended maintenance doses are 5, 10 and 15 mg. More people stopped because of stomach side effects at 15 mg than at 5 mg.4

Does the NHS stop Mounjaro if I stop losing weight?

NICE asks for a decision on continuing if under 5% is lost after 6 months on the highest tolerated dose. It isn’t automatic.7

Will I regain weight if I stop at a plateau?

In SURMOUNT-4, people switched to a dummy injection regained 14.8% of their weight over a year.4

How we researched this

On 14 October 2026 we read the UK labels for Mounjaro and Wegovy, the SURMOUNT-1 paper, a 2025 post-hoc analysis of plateau timing, a 2025 nutrition advisory, an appetite study and NICE TA1026 and NG246.

The plateau analysis was written mostly by Lilly staff and only included people who kept taking Mounjaro and lost at least 5%. Kilogram examples are our arithmetic.

Before you move on

  • Expect weight loss to slow and level off.
  • Know your 5% figure: starting weight divided by 20.
  • Note when you reached your current dose.
  • Keep up protein, strength work and activity.
  • Talk to your prescriber before changing or stopping.
Doctor questionsLife on a GLP‑1Stopping and the long term

More from the UK blog

UKUnited KingdomWhat is the NICE 5% rule, and when does the NHS stop a weight-loss jab?UKUnited KingdomWhat happens when you stop Mounjaro or Wegovy?UKUnited KingdomWhat are the side effects of Mounjaro, and how do you report them?
About GLP Guidebook

The monthly UK update

An independent guide to GLP‑1 medicines. We don’t sell medicines, take drug-company money, earn commissions or link to any provider. Once a month: NHS changes, approvals, list prices and safety alerts. How we write

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Sources

  1. Horn DB et al. Time to weight plateau with tirzepatide treatment in the SURMOUNT-1 and SURMOUNT-4 clinical trials. Clin Obes 2025;15(3):e12734. Post-hoc analysis; most authors are Eli Lilly employees. doi:10.1111/cob.12734. PMID 39800653. PubMed
  2. Mozaffarian D et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Am J Clin Nutr 2025;122:344–367. PMID 40450457. PMC12612741. PubMed
  3. Polidori D et al. How strongly does appetite counter weight loss? Quantification of the feedback control of human energy intake. Obesity 2016;24(11):2289–2295. PMID 27804272. PubMed
  4. Eli Lilly. Mounjaro KwikPen: UK summary of product characteristics (SmPC), electronic Medicines Compendium. Date of revision 29 August 2026. Sections 4.2 (doses, the 5% check, missed doses), 4.8 and 5.1 (SURMOUNT-1 and SURMOUNT-4 tables). UK label. medicines.org.uk (emc)
  5. Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205–216. 2,539 adults, 72 weeks. Funded by Eli Lilly. PMID 35658024. PubMed
  6. Novo Nordisk. Wegovy FlexTouch: UK summary of product characteristics (SmPC), electronic Medicines Compendium. Date of revision 09/2026. Sections 4.2 (the 5% check) and 5.1 (STEP 1 and STEP 2 tables). UK label. medicines.org.uk (emc)
  7. NICE. Tirzepatide for managing overweight and obesity, TA1026, recommendation 1.2. nice.org.uk
  8. NICE. Overweight and obesity management (NG246), chapter “Medicines and surgery”, recommendations 1.17.6 and 1.17.7. Last updated 8 January 2026. nice.org.uk
  9. MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know. Guidance, updated 5 February 2026. gov.uk
  10. MHRA. MHRA updates guidance for GLP-1 prescribers and patients (acute pancreatitis). Press release, 29 January 2026. gov.uk
  11. NHS. When to call 999, and NHS 111 if you’re not sure. nhs.uk
  12. nidirect (Northern Ireland). GP out of hours service. nidirect.gov.uk
  13. MHRA. First GLP-1 tablet for weight loss approved in the UK. Press release, 11 June 2026 (“As with all GLP-1 receptor agonists, this is a prescription-only medication”). gov.uk

Last checked 14 Oct 2026 · Next review due 14 Oct 2027 · Report an error

How this page was made. Written by the GLP Guidebook team from the sources above. It’s general information, not medical advice. Talk to your GP, pharmacist or prescriber before starting, stopping or changing any medicine. We don’t sell, prescribe or recommend any brand or provider. How we write