Results & Expectations

Mounjaro Results

Learn what results to expect from Mounjaro, including weight loss timelines, average outcomes, and how progress typically develops.

Whether you are considering Mounjaro or already on it and trying to gauge your own results against the trial data, this guide breaks down the published clinical-trial weight-loss numbers for tirzepatide at each licensed dose. The figures come from the SURMOUNT-1 obesity trial and the head-to-head SURMOUNT-5 trial against semaglutide. LetsLoseWeight is an independent comparison site; we do not prescribe medication, and individual results vary widely.

The headline number from SURMOUNT-1

The pivotal trial for tirzepatide in weight management was SURMOUNT-1, published in the New England Journal of Medicine in 2022. Adults with obesity but without type 2 diabetes were randomised to placebo or one of three tirzepatide doses for 72 weeks. All participants followed lifestyle interventions including a reduced-calorie diet and increased physical activity (Jastreboff et al., NEJM 2022).

Average weight loss at 72 weeks:

Dose Average weight loss Average weight loss in kg (≈)
Placebo 3.1% ~3 kg
Tirzepatide 5mg 15.0% ~15 kg
Tirzepatide 10mg 19.5% ~20 kg
Tirzepatide 15mg 20.9% ~21 kg

These are means from a population whose average starting weight was around 105kg. Personal results scale roughly with starting weight — someone starting at 80kg should not expect to lose 21kg on 15mg, but a similar percentage is plausible.

What the spread looked like

The trial averages compress a wide spread of outcomes. On the 15mg dose:

  • Around 57% of participants lost at least 20% of their starting weight
  • Around 36% lost at least 25%
  • Around 9% lost less than 5% — what the trial called "non-responders"
  • A small percentage lost 30% or more

On the 5mg dose, the proportion losing 20% or more was lower (around 30%) but still substantial. Even on the lowest licensed maintenance dose, the majority of patients lost a clinically meaningful amount.

Trial population — who was studied

SURMOUNT-1 enrolled around 2,500 adults with the following profile:

  • Mean age around 45 years
  • Mean BMI around 38 kg/m²
  • Mean starting weight around 105 kg
  • Roughly two-thirds female
  • Without type 2 diabetes

Patients with type 2 diabetes were studied in a separate trial (SURMOUNT-2), which produced somewhat smaller average weight loss — typical of obesity-treatment trials, where diabetes appears to slightly reduce the response.

Beyond weight — what else changed

The SURMOUNT-1 trial also reported on cardiometabolic markers. By 72 weeks, the higher-dose tirzepatide groups showed:

  • Reductions in waist circumference averaging 13–18 cm
  • Improvements in blood pressure — typical reductions of 5–8 mmHg systolic
  • Improvements in fasting blood sugar even in non-diabetic participants
  • Improvements in lipid panel — including triglycerides and HDL cholesterol
  • Improvements in liver enzymes (ALT) and markers of insulin resistance

The medicine's broader effects on cardiometabolic health are part of why it is being studied for cardiovascular outcomes (the SURMOUNT-MMO trial) and other obesity-related conditions.

Mounjaro vs Wegovy — the head-to-head

The SURMOUNT-5 trial in 2025 was the first head-to-head comparison of tirzepatide and semaglutide for weight management. After 72 weeks, average weight loss was greater with tirzepatide than with semaglutide, with both producing clinically meaningful weight loss (Aronne et al., NEJM 2025).

That does not mean Mounjaro is the right choice for everyone. Some patients lose more on semaglutide than on tirzepatide; tolerability differs; and choice depends on cost, eligibility and prescriber assessment. See our Mounjaro vs Wegovy UK comparison.

Real-world results vs trial results

Real-world data on tirzepatide tends to show slightly lower average weight loss than the SURMOUNT trials. This is normal across most medicines: trial conditions are more controlled, monitoring is more intensive, and trial populations are more selected. As a rough rule of thumb, real-world averages tend to be 70–85% of trial averages.

For tirzepatide at 15mg, where the trial average was around 21%, real-world averages tend to be in the 15–18% range. Still substantial, but a step below the headline figure.

What this means for setting expectations on Mounjaro

A reasonable, evidence-based set of expectations:

  • Most patients on Mounjaro lose a clinically meaningful amount of weight — typically 12–20% of starting weight at the maintenance dose, over 12–18 months
  • Some patients lose more — particularly those who tolerate higher doses and engage strongly with lifestyle changes
  • Some patients lose less — and a small minority do not respond meaningfully
  • The dose matters but isn't everything — diet, activity, sleep, stress and individual biology all shift the curve

When results don't match expectations

A reasonable benchmark from clinical practice is at least 5% weight loss by 12 weeks at the maintenance dose. If your trajectory is below that, possible reasons to discuss with your prescriber:

  • Adherence — keeping weekly injections on schedule
  • Whether the dose can be titrated higher (most non-responders are on lower doses)
  • Other medicines that promote weight gain (some antidepressants, some antipsychotics, some diabetes medicines)
  • Untreated medical conditions (hypothyroidism, sleep apnoea, depression)
  • Calorie reduction — the medicine reduces appetite but cannot fully override active overconsumption

For more, see our what affects results guide and plateau guide.

Long-term — what happens after 18 months

The trial period was 72 weeks. Beyond that, real-world experience and trial extensions suggest:

  • Most patients who continue treatment maintain their weight loss at the new lower level
  • Weight loss usually slows substantially by month 12–18 as the body finds a new set point
  • Stopping tirzepatide is associated with weight regain — tirzepatide-specific withdrawal data is more limited than the equivalent semaglutide data, but published trials follow a similar pattern
  • Treatment is generally framed as long-term — analogous to medicines for blood pressure or cholesterol

Frequently asked questions

Should I expect to lose 21% of my starting weight on Mounjaro?
That is the trial average at the 15mg dose. Many patients lose more, many lose less, and real-world averages tend to be a bit lower than the trial figure. Expect a range of 15–20% on full dose, recognising the spread is wide.

How quickly should I see Mounjaro results?
Most patients see appetite changes within 1–2 weeks and measurable scale changes by weeks 5–8. The steepest weight-loss curve is typically months 4–9. See our when do you see results guide for more detail.

Why might my results be lower than the trial average?
Real-world results tend to run lower than trial results across most medicines. Other factors include lower dose tolerated, less consistent diet and activity changes, untreated medical conditions, and individual biological variability.

Can I expect to keep losing weight after 18 months?
The rate of loss slows substantially in the second year. Most patients stabilise at a new lower set point by 12–18 months. Continued small losses are common but the steep weight-loss phase is typically over.

Is Mounjaro better than Wegovy for results?
On average, yes — SURMOUNT-5 showed greater average weight loss with tirzepatide. But individual response varies, and the right medicine for you depends on tolerability, eligibility and prescriber recommendation as well as average results.

Next steps

Sources

This guide is for general information only and is not a substitute for professional medical advice. Individual results vary. Talk to a qualified prescriber about realistic expectations for your situation.

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Mounjaro Results UK: Trial Data and Expected Loss | LetsLoseWeight