How Much Weight Can You Lose on Mounjaro? (2026)

## Quick answer

At the 15mg maintenance dose, the SURMOUNT-1 clinical trial showed an average weight loss of 22.5% of body weight over 72 weeks, around 22.5kg for someone starting at 100kg. At lower doses, average weight loss was 16.0% at 5mg and 21.4% at 10mg. Results vary between individuals, and are typically highest when treatment is combined with dietary changes and regular activity.

## What the clinical trials show

The primary evidence base for Mounjaro (tirzepatide) in weight management is SURMOUNT-1, published in the *New England Journal of Medicine* in 2022 (ClinicalTrials.gov: NCT04184622). The trial enrolled 2,539 non-diabetic adults with obesity, or overweight plus at least one weight-related comorbidity. Participants were randomised 1:1:1:1 to tirzepatide 5mg, 10mg, 15mg, or placebo, alongside a structured lifestyle intervention: a 500 kcal daily deficit and 150 minutes per week of physical activity. Tirzepatide was initiated at 2.5mg and escalated by 2.5mg every four weeks to the assigned dose.

SURMOUNT-1 reports two estimands. The efficacy estimand reflects results in participants who adhered to treatment as intended, and is the figure most commonly cited in clinical communications. The treatment-regimen estimand reflects all randomised participants regardless of adherence, and is the more conservative figure. Both come from the same published trial. Headline outcomes are shown below.

### Efficacy estimand (adherers)

| Dose | Average weight loss | Lost 5%+ | Lost 10%+ | Lost 15%+ | Lost 20%+ | Lost 25%+ |
|---|---|---|---|---|---|---|
| 5mg | 16.0% | 89% | 73% | 50% | 32% | 16.5% |
| 10mg | 21.4% | 96% | 86% | 74% | 55% | 35% |
| 15mg | 22.5% | 96% | 90% | 78% | 63% | 39.7% |
| Placebo | 2.4% | 28% | 14% | 6% | 1.3% | 0.3% |

Treatment-regimen estimand results were 15.0% at 5mg, 19.5% at 10mg, 20.9% at 15mg and 3.1% on placebo.

Waist circumference fell by an average of 14.6cm at 5mg, 19.4cm at 10mg and 19.9cm at 15mg, compared with 3.4cm on placebo.

### SURMOUNT-2 (adults with type 2 diabetes)

SURMOUNT-2 enrolled 938 adults with overweight or obesity and type 2 diabetes over 72 weeks. Mean weight loss was 13.4% at 10mg and 15.7% at 15mg, compared with 3.3% on placebo. Weight loss is typically lower in adults with type 2 diabetes than in non-diabetic populations. This pattern is consistent across GLP-1 and dual GLP-1/GIP receptor agonist medicines, and reflects metabolic differences between the two groups.

### Three-year follow-up data

An extended follow-up of SURMOUNT-1, updated in December 2024, reports outcomes through week 176 (around 3.4 years of continuous treatment). Weight loss was substantially maintained: 12.3% at 5mg, 18.7% at 10mg and 19.7% at 15mg. A secondary finding with notable clinical implications: participants on the 15mg dose had a 94% lower rate of new-onset type 2 diabetes compared with placebo, at 0.4% versus 13.3%. Participants who stopped treatment after week 176 regained a significant proportion of lost weight during the subsequent 17-week off-treatment period.

## What does this mean in real terms?

The table below converts the trial averages into kilograms for a range of starting weights.

| Starting weight | 16.0% loss (5mg) | 21.4% loss (10mg) | 22.5% loss (15mg) |
|---|---|---|---|
| 80kg | 12.8kg | 17.1kg | 18.0kg |
| 90kg | 14.4kg | 19.3kg | 20.3kg |
| 100kg | 16.0kg | 21.4kg | 22.5kg |
| 110kg | 17.6kg | 23.5kg | 24.8kg |
| 120kg | 19.2kg | 25.7kg | 27.0kg |
| 130kg | 20.8kg | 27.8kg | 29.3kg |

These figures are trial averages. Individual response varies. SURMOUNT-1 recorded weight reductions ranging from under 5% to over 30% across participants. Some respond strongly at 5mg or 10mg and never need to escalate. Others plateau at mid-range doses. This variation reflects individual biology rather than effort or adherence.

Trial participants also followed a structured lifestyle intervention alongside the treatment, and this context matters. Adults who make meaningful changes to diet and activity alongside Mounjaro consistently achieve better outcomes than those who rely on the treatment alone.

## When do results happen: the timeline

| Timeframe | What typically happens |
|---|---|
| Weeks 1 to 4 (2.5mg) | Adjustment phase. Appetite begins to reduce. Little weight change. |
| Month 2 (5mg) | First therapeutic dose. Appetite suppression becomes more pronounced. Early weight loss begins. |
| Months 3 to 4 (7.5mg, 10mg) | Visible weight loss for most patients. Dose continues to escalate. |
| Months 5 to 6 (12.5mg, 15mg) | Approaching maintenance dose. Continued weight loss. |
| Month 6 onwards (15mg) | Maximum dose reached. Continued loss at a slower rate. |
| Months 6 to 12 | Greatest cumulative weight loss for most patients. |
| Months 12 to 18+ | Weight loss continues at a slower rate, approaching nadir. |

A plateau analysis of SURMOUNT-1 published in 2025 found the greatest rate of weight loss occurred in the first 24 weeks, during dose escalation. Mean loss across BMI categories in that period was between 13% and 14%. A further 7% to 10% was typically achieved between weeks 24 and 72 in participants with higher baseline BMI. Median time to plateau was 24 to 36 weeks, depending on BMI category.

The 2.5mg starting dose is an adjustment phase, not a therapeutic dose. Adults who stop in the first month because they see little weight change are stopping before the treatment has had time to work. Most patients do not reach their first therapeutic dose until week 4, when the dose moves to 5mg.

## What affects how much weight you lose on Mounjaro?

**Dose reached.** Higher doses produced greater average weight loss in the trial data: 22.5% at 15mg versus 16.0% at 5mg. However, many adults achieve excellent results at 5mg or 10mg and do not need to escalate. There is no clinical requirement to reach 15mg. Escalation is appropriate when response at a lower dose is insufficient.

**Diet and activity.** SURMOUNT-1 used a structured lifestyle intervention, and those patterns were associated with the trial outcomes. Mounjaro reduces appetite significantly, but the quality of what is eaten still matters. Prioritising protein to preserve muscle mass during weight loss, and reducing ultra-processed food, consistently improves outcomes alongside the treatment.

**Individual biology.** GLP-1 and GIP receptor sensitivity varies between individuals. SURMOUNT-1 recorded weight reductions ranging from under 5% to over 30% on the same dose. This variation is biological, not a measure of effort or adherence.

**Duration of treatment.** Three-year data from SURMOUNT-1 shows weight loss is substantially maintained with continued treatment. Stopping early, before reaching a therapeutic dose or before the full effect has developed, significantly reduces total weight lost.

## What happens if you stop taking Mounjaro?

The three-year SURMOUNT-1 follow-up included a 17-week off-treatment period after week 176. Participants who stopped regained a significant proportion of lost weight during this period. The pattern mirrors what has been seen with semaglutide in the STEP-4 trial.

Obesity is a chronic condition. Mounjaro treats it while the treatment continues, in the same way antihypertensive medicines treat blood pressure while they are taken. When treatment stops, the underlying condition reasserts itself. Most adults who achieve meaningful results continue long-term.

One further point from the three-year data is worth raising with a prescriber: participants on 15mg had a 94% lower rate of new-onset type 2 diabetes compared with placebo, at 0.4% versus 13.3%. Sustained treatment may offer benefits beyond weight management, particularly for adults at higher metabolic risk. Any decision to stop should be discussed with a prescriber first.

## Safety update

In January 2026, the MHRA updated its product information for GLP-1 and dual GLP-1/GIP receptor agonist medicines to highlight a small risk of severe acute pancreatitis, including rare reports of necrotising and fatal pancreatitis. The MHRA has described these medicines as safe and effective for the vast majority of patients. Anyone experiencing severe, persistent stomach pain (particularly pain radiating to the back, with nausea or vomiting) should seek urgent medical attention. Suspected side effects can be reported via the [Yellow Card scheme](https://yellowcard.mhra.gov.uk/).

## Mounjaro and Wegovy: what the data shows

Mounjaro (tirzepatide) and Wegovy (semaglutide) are both licensed in the UK for weight management, and both produced clinically significant weight loss in their respective trials. Different populations and trial designs mean the figures below should be read as the outcomes of separate studies, not as a direct head-to-head comparison.

In SURMOUNT-1, participants on tirzepatide 15mg lost an average of 22.5% of body weight over 72 weeks. In STEP-1, participants on semaglutide 2.4mg lost an average of 14.9% over 68 weeks. More recently, the STEP UP trial evaluated a higher 7.2mg semaglutide dose and reported mean weight loss of 20.7% over 72 weeks (efficacy estimand). Wegovy is typically £50 to £100 per month cheaper than Mounjaro at comparable dose stages. Some adults respond better to one treatment than the other. Individual biology plays a meaningful role, and the choice is best made with a prescriber.

For a clinical and pricing comparison, read [What is Wegovy? What is Mounjaro?](https://www.myfoundry.co.uk/blogs/news/what-is-wegovy-what-is-mounjaro).

## How to access Mounjaro in the UK

On private prescription, Mounjaro is available for adults with a BMI of 30 or above. It is also available for adults with a BMI of 27 or above who have at least one weight-related comorbidity, such as type 2 diabetes, hypertension, or cardiovascular disease. Adjusted BMI thresholds apply for certain ethnic backgrounds, in line with NICE guidance.

NHS access began as a phased rollout in June 2025. Current Phase 1 eligibility is restrictive: BMI 40+ (or 37.5+ for certain ethnic groups) with four or more qualifying conditions. From April 2026, tirzepatide prescribing for obesity sits within the GP QOF contract, with practice participation optional. Most adults with a BMI between 30 and 39 do not currently qualify on the NHS, and will need a private prescription if they want to start treatment in 2026.

At Foundry, the health assessment takes around five minutes. If you meet the clinical criteria, a UK-registered prescriber reviews your information and, where appropriate, prescribes treatment. Your order is dispensed by our GPhC-registered pharmacy partner and delivered by tracked cold-chain shipping. The Mounjaro 2.5mg starter dose is £168 per month on PAYG, which covers clinical assessment, prescribing, needles, and a sharps bin on the first order. With Forge annual membership, medication-only is £139 per month plus a £249 annual fee, which covers all service fees across the membership year. Shipping is charged separately at checkout.

For a full breakdown of routes and prices, read the [cheapest way to get Mounjaro in the UK guide](https://www.myfoundry.co.uk/pages/what-is-the-cheapest-way-to-get-mounjaro-in-the-uk-2026-guide).

## Frequently asked questions

### How much weight can I lose on Mounjaro?

In SURMOUNT-1, adults taking tirzepatide 15mg lost an average of 22.5% of body weight over 72 weeks, around 22.5kg for someone starting at 100kg. Average weight loss was 16.0% at 5mg and 21.4% at 10mg. Individual results vary. Some adults lose considerably more than the average, others less. Dose reached, diet, activity and individual biology all influence the outcome. Three-year follow-up data shows weight loss is substantially maintained with continued treatment.

### How long does it take to see results on Mounjaro?

Most adults notice a significant reduction in appetite within the first two to four weeks. Visible weight loss typically begins from month two, as the dose increases from the initial 2.5mg to 5mg. The greatest rate of weight loss occurs in the first 24 weeks, during dose escalation. Results continue to build through month 12 and beyond, with most adults reaching their lowest weight between months 9 and 18.

### Is 22.5% weight loss typical on Mounjaro?

The 22.5% figure is the average weight loss at the 15mg dose in SURMOUNT-1, among participants who adhered to treatment as intended. Individual results range from under 5% to over 30%. In the trial, 39.7% of participants on 15mg lost 25% or more of their body weight, while a minority responded less strongly. The average is a useful reference point, not a guaranteed outcome.

### How does Mounjaro compare with Wegovy for weight loss?

In their respective trials, tirzepatide 15mg produced 22.5% mean weight loss over 72 weeks (SURMOUNT-1). Semaglutide 2.4mg produced 14.9% over 68 weeks (STEP-1), and semaglutide 7.2mg produced 20.7% over 72 weeks (STEP UP). Trial populations and designs differ, so these figures should be read as separate studies rather than a direct comparison. Wegovy is typically £50 to £100 per month cheaper at comparable dose stages. Some adults respond better to one than the other.

### Will I regain weight if I stop taking Mounjaro?

Three-year SURMOUNT-1 data showed that adults who stopped tirzepatide after extended treatment regained a significant proportion of lost weight during the subsequent off-treatment period. The same pattern has been seen with semaglutide in STEP-4. Obesity is a chronic condition, and these treatments work while they are taken. Most adults who achieve meaningful results continue long-term. Any decision to stop should be discussed with a prescriber first.

### Am I eligible for Mounjaro in the UK?

On private prescription, Mounjaro is available for adults with a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related comorbidity such as type 2 diabetes, hypertension, or cardiovascular disease. Adjusted BMI thresholds apply for certain ethnic backgrounds, in line with NICE guidance. NHS access began in June 2025 and currently requires BMI 40+ with four qualifying conditions. Most adults who would benefit from Mounjaro will need a private prescription in 2026.

## Next step

Ready to start Mounjaro with a regulated UK provider? Foundry is a CQC-regulated telehealth service. A five-minute health assessment is the starting point. If you meet the clinical criteria, a UK-registered prescriber reviews your information and, where appropriate, prescribes treatment dispensed by our GPhC-registered pharmacy partner.

[Check your eligibility](https://www.myfoundry.co.uk/pages/start-a-consultation)

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*Treatment is subject to prescriber approval and clinical suitability. Results vary between individuals. Trial figures are from published clinical studies and may not reflect individual outcomes. Shipping is charged separately at checkout.*