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
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Average Monthly Weight Loss on Mounjaro
Most people taking Mounjaro don't lose weight at a constant rate each month — weight loss typically accelerates as your dose increases over the first 4–5 months, then stabilises at maintenance doses. Clinical trial data from the SURMOUNT studies showed an average total weight loss of around 15–21% of body weight over 72 weeks, but monthly losses vary significantly. This guide breaks down what the evidence shows and what to realistically expect during your treatment journey on this prescription weight management injection.
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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.
How Mounjaro Dose Titration Affects Monthly Weight Loss
Mounjaro uses a gradual dose titration schedule, which means your dose increases every 4 weeks. This affects your monthly weight loss pattern:
- Weeks 1–4 (2.5 mg): Modest weight loss, typically 1–2 kg in month one as your body adjusts
- Weeks 5–8 (5 mg): Weight loss accelerates, average 2–3 kg in month two
- Weeks 9–12 (7.5 mg): Further acceleration, approximately 2.5–3.5 kg in month three
- Weeks 13+ (10 mg and above): Weight loss typically plateaus as your body acclimatises to the medication, averaging 1–2 kg per month at maintenance doses
These are clinical averages — individual responses vary considerably. Some people lose more, others less. Use our GLP-1 weight loss calculator to see projected results based on dose and your starting weight.
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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.
Clinical Trial Evidence: SURMOUNT Data
The SURMOUNT-1 clinical trial tracked weight loss in adults over 72 weeks (approximately 16 months). At the maximum 15 mg dose, participants lost an average of 20.9% of their body weight — but this breaks down to roughly 1.3 kg per month on average across the entire study period. In early months (weeks 1–12), losses were typically higher; at maintenance doses (weeks 17 onwards), monthly losses slowed to approximately 0.5–1 kg per month. Remember: clinical trial participants also followed a reduced-calorie diet and increased physical activity — weight loss medication works alongside, not instead of, lifestyle changes. Your GP or prescriber can discuss what's realistic for your specific circumstances.
- 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 will I lose per month on Mounjaro?
Monthly weight loss varies by dose, individual metabolism, and lifestyle factors. Expect 1–2 kg in month one, 2–3.5 kg in months two to four as your dose increases, then 0.5–2 kg per month at maintenance doses. The SURMOUNT-1 trial showed an average of 20.9% total body weight loss over 16 months, roughly 1.3 kg monthly on average.
Why is monthly weight loss faster at the start?
Your dose increases every 4 weeks, so your body experiences stronger appetite-suppressing effects as the dose titrates upward. Once you reach your maintenance dose (typically 10–15 mg), your body adapts and monthly losses plateau. This is normal and expected.
What if I'm not losing weight as expected?
Individual results vary due to genetics, metabolism, other medications, and adherence to diet and exercise. If weight loss is slower than expected after 8–12 weeks, discuss this with your GP or prescriber — they may adjust your dose, review your lifestyle approach, or investigate underlying factors affecting weight loss.
Is 1–2 kg per month sustainable long-term on Mounjaro?
Yes, 0.5–1 kg per week (2–4 kg monthly) is considered safe and sustainable according to NHS guidelines. Most people on maintenance Mounjaro doses see monthly losses of 0.5–2 kg, which is healthy. gradual weight management can lead to muscle loss and nutritional deficiencies.
How do I track my monthly progress accurately?
Weigh yourself weekly at the same time of day (morning, before eating) and record the results. Use our free progress tracker to log your weight journey — this helps you spot trends over weeks and months rather than fixating on daily fluctuations, which are normal and don't reflect true fat loss.
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.