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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What BMI Qualifies for Mounjaro in the UK?
In the UK, Mounjaro (tirzepatide) is available for adults with a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions. These are the NHS-aligned eligibility criteria set by NICE. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply because these groups face higher health risks at lower weights. Eligibility is assessed individually by a prescriber following a clinical assessment — your personal health circumstances matter, not just your BMI number alone.
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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.
NHS BMI Categories and NICE Eligibility Guidance
The NHS BMI categories form the foundation of Mounjaro eligibility in the UK. According to NICE guidance, Mounjaro (tirzepatide) may be prescribed to adults who meet specific BMI thresholds:
- BMI 30 or above — eligible for prescription
- BMI 27–29.9 — eligible if you have at least one weight-related health condition, such as type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, sleep apnoea, or a history of heart disease or stroke
For comparison, the NHS defines a healthy BMI range as 18.5–24.9. A BMI of 25–29.9 falls into the overweight category, while BMI 30–34.9 is obese (Class I). Calculate your personal BMI using our free BMI calculator above to see where you fall within these categories. It's important to note that BMI has limitations — it doesn't distinguish between muscle and fat, so your actual health profile may differ from your BMI alone.
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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.
NHS Weight Management Pathway and How to Access Support
In the UK, prescription weight management medications like Mounjaro are typically accessed through the NHS weight management pathway. This usually means referral to a specialist tier 3 weight management service, which your GP can arrange. However, access varies significantly by region (ICB), and some areas have substantial waiting lists. Alternatively, Mounjaro is available through private prescribing services following an online clinical assessment with a UK-licensed prescriber. Whether through NHS or private routes, eligibility is confirmed individually based on your BMI, health conditions, and overall health profile. Your GP or prescriber will assess whether Mounjaro is appropriate for you. Try our free GLP-1 weight loss calculator to explore potential outcomes alongside these criteria.
- 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.
What is the minimum BMI to qualify for Mounjaro on the NHS?
The minimum BMI for Mounjaro eligibility is typically 30 or above. If your BMI is 27–29.9, you may qualify if you have a weight-related health condition such as type 2 diabetes, high blood pressure, sleep apnoea, or heart disease history. Eligibility is assessed individually by a prescriber.
Do different BMI thresholds apply if I'm South Asian or Black African?
Yes. The NHS recommends lower BMI thresholds for South Asian, Chinese, Black African, and Black Caribbean adults because these groups face higher health risks at lower weights. You may be eligible at a lower BMI than standard thresholds — discuss this with your GP or prescriber.
What health conditions count as "weight-related" for Mounjaro eligibility?
Weight-related health conditions include type 2 diabetes, prediabetes, high blood pressure (hypertension), abnormal blood fats (dyslipidaemia), obstructive sleep apnoea, and a history of heart attack, stroke, or cardiovascular disease. Your GP will assess whether you have qualifying conditions.
Can I get Mounjaro on the NHS if I'm overweight but below BMI 27?
Unlikely. NHS NICE guidance specifies BMI 27 or above (with conditions) or BMI 30 or above (without conditions). If your BMI is below 27, discuss your individual circumstances with your GP — they may offer other weight management support through the NHS pathway.
What's the difference between NHS and private access to Mounjaro based on BMI?
BMI eligibility criteria are similar, but NHS access requires referral to specialist services with potential waiting lists, while private prescribing offers faster access following an online assessment. Both require clinical assessment; BMI alone doesn't assures prescription.
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.