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
How Much Weight Do You Lose With Mounjaro?
Weight loss with Mounjaro varies significantly between individuals, but clinical trial data provides realistic expectations. On average, people lose between 15% and 21% of their body weight over 72 weeks when using Mounjaro alongside a reduced-calorie diet and increased physical activity. Your actual results depend on your starting weight, dose, lifestyle changes, and individual metabolism. This guide explains what the evidence shows and the factors that influence your personal outcome.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Average Weight Loss by Mounjaro Dose (Clinical Trial Data)
The SURMOUNT-1 clinical trial tracked weight loss results across different Mounjaro doses over 72 weeks. Participants combined medication with a structured diet plan and exercise programme:
- 5 mg dose: Average weight loss of approximately 15% of body weight
- 10 mg dose: Average weight loss of approximately 19.5% of body weight
- 15 mg dose (maximum): Average weight loss of approximately 20.9% of body weight
To put this in perspective, if you weigh 100 kg at the start, a 15% loss equals 15 kg (2 stone 5 lbs), whilst a 20.9% loss equals approximately 21 kg (3 stone 4 lbs). However, individual results vary considerably — some people lose more, others less. Your GLP-1 weight loss calculator can help estimate potential weight loss ranges based on your starting weight and dose.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Factors That Affect Your Personal Weight Loss
Several factors influence how much weight you personally lose with Mounjaro, beyond the average trial results. Starting weight: People with higher starting weights often lose more kg in absolute terms. Age and metabolism: Metabolic rate naturally slows with age, affecting the pace of loss. Genetic factors: Some people respond more effectively to GLP-1 medication than others. Adherence to lifestyle changes: Mounjaro works best alongside reduced calorie intake and regular physical activity — weight loss plateaus without these changes. Medical conditions: Diabetes, thyroid conditions, and PCOS can affect outcomes. Your GP or prescriber can discuss realistic expectations based on your specific health profile.
- 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.
Can I lose 1 stone per month with Mounjaro?
Weight loss varies individually, but losing 1 stone per month is very rapid and not typical. Clinical trials show average loss of 0.2–0.4 kg per week (about 0.8–1.6 lbs weekly). The NHS recommends sustainable loss of 0.5–1 kg per week. Faster loss risks muscle loss and other health impacts. Your prescriber can advise safe, realistic expectations for your circumstances.
How long before you see results with Mounjaro?
Most people notice initial changes within 2–4 weeks — typically reduced appetite and changed food preferences. Measurable weight loss usually appears after 4–8 weeks. The SURMOUNT trial measured results over 72 weeks (about 18 months). Weight loss is a gradual process; expect steady progress rather than rapid drops. Use our free progress tracker to monitor your journey week by week.
What if I don't lose as much weight as others on Mounjaro?
Individual response to Mounjaro varies considerably due to genetics, metabolism, lifestyle factors, and adherence to diet and exercise. Some people lose 25% of body weight; others lose 10%. This doesn't mean the medication isn't working — your body may be responding differently. Discuss your results with your prescriber; dose adjustments or lifestyle modifications may help.
Does Mounjaro weight loss plateau or continue indefinitely?
Weight loss typically follows a curve — faster initially, then slowing over time as your body adjusts. Most people reach a plateau within 12–24 months. This is normal. Continuing the medication helps maintain your loss rather than achieving further loss. Your prescriber will discuss long-term management and when to consider stopping or maintaining your current dose.
Can I work out what my healthy weight should be?
Your healthy weight range depends on your height and is defined by a BMI of 18.5–24.9 according to NHS guidelines. Use our free BMI calculator to find your personal healthy weight range — it accounts for your specific height. For South Asian or Black African heritage, slightly lower ranges apply. Your GP can also advise on realistic, healthy targets based on your individual health profile.
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.