The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Average Weight Loss Per Week On Mounjaro
Clinical trials showed that people using Mounjaro (tirzepatide) lose weight at different rates depending on dose, lifestyle, and individual metabolism. On average, participants lost between 0.5 to 1.5 kg per week during the SURMOUNT-1 trial, though individual results vary significantly. This guide explains the evidence, how Mounjaro works, and how your current BMI affects what a healthy weight loss rate looks like for you personally. The NHS recommends losing no more than 0.5 to 1 kg per week for sustainable results.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Clinical Trial Data and Average Weekly Weight Loss
In the SURMOUNT-1 clinical trial, participants using Mounjaro achieved an average total weight loss of 15% to 21% of body weight over 72 weeks — depending on dose escalation. This translates to approximately 0.5 to 1.5 kg per week on average, though results were not linear (weight loss was faster in earlier weeks, then plateaued). At the 5 mg dose, average loss was around 15%; at 10 mg, approximately 19.5%; and at the maximum 15 mg dose, around 20.9%. However, these are clinical trial averages achieved alongside a reduced-calorie diet and increased physical activity. Individual results vary considerably — some participants lost more, others less. Factors affecting your personal rate include: starting weight, age, metabolism, how closely you follow dietary guidance, and how much physical activity you increase. Your GP or prescriber can discuss realistic expectations based on your individual health profile.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Healthy Weight Loss Rate and Your BMI Target
The NHS advises that sustainable weight loss is 0.5 to 1 kg per week. If you're using Mounjaro, your weight loss rate may initially exceed this (especially in the first 4–8 weeks), then stabilise. To understand what your ideal weight range should be, calculate your BMI using your current height and weight — use our free BMI calculator above to check instantly. A healthy BMI for UK adults is 18.5 to 24.9 (or 18.5 to 22.9 for South Asian, Chinese, Black African, and Black Caribbean adults). Once you know your target BMI range, you can calculate the healthy weight range for your height, then work backwards to estimate how many weeks sustainable loss might take. For example, if you're 1.75m tall with a BMI of 32, your healthy weight range is 56–76 kg — meaning a loss of about 10–20 kg depending on your starting point. At 0.75 kg per week, this could take 13–27 weeks to achieve safely.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How much weight should I expect to lose per week on Mounjaro?
Clinical trials showed average weight loss of 0.5 to 1.5 kg per week, but this varies widely between individuals. The NHS recommends 0.5 to 1 kg per week as sustainable. Your actual rate depends on starting weight, dose, diet adherence, activity level, and metabolism. Your prescriber can discuss realistic expectations for your situation.
Is faster weight loss on Mounjaro better?
No. Faster weight loss (over 1.5 kg per week) can lead to muscle loss, nutrient deficiency, and gallstones. The NHS recommends gradual loss of 0.5 to 1 kg weekly. Mounjaro works best alongside consistent dietary changes and exercise, not as a quick-fix solution.
Why do people lose more weight in the first weeks of Mounjaro?
Initial weight loss includes water weight and glycogen depletion, not just fat loss. This is why the first 2–4 weeks often show faster results. After this, weight loss typically slows to a steadier rate. This is normal and not a sign that the medication is becoming less effective.
How do I know if my weight loss rate on Mounjaro is healthy?
Use our free BMI calculator to track your BMI progress — aim for movement towards the 18.5 to 24.9 range. Losing 0.5 to 1 kg per week is healthy. If you're losing faster, discuss this with your GP. Track your progress using our free progress tracker to monitor trends over weeks, not daily fluctuations.
Can I calculate my target weight loss timeline using Mounjaro?
Yes. First, calculate your healthy weight range using the BMI calculator — a BMI of 18.5 to 24.9 is healthy for UK adults. Find the difference between your current weight and target weight, then divide by your expected weekly loss rate (typically 0.5–1 kg). Always discuss timelines with your prescriber, as individual results vary based on lifestyle and dose escalation.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.