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 do you need for Mounjaro in the UK?
To be eligible for Mounjaro (tirzepatide) in the UK, you typically need a BMI of 30 or above, or a BMI of 27–29.9 if you have weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply due to higher health risks at lower BMI levels. Your GP or a licensed prescriber will assess your individual eligibility following a clinical assessment. Use our free BMI calculator above to check your personal BMI instantly.
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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.
BMI ranges and Mounjaro eligibility in the UK
According to NHS guidelines and UK prescribing criteria, the BMI formula is: weight (kg) ÷ height (m)². The standard BMI categories UK classification is:
- BMI below 18.5: Underweight
- BMI 18.5–24.9: Healthy weight
- BMI 25.0–29.9: Overweight
- BMI 30.0–34.9: Obese (Class I)
- BMI 35.0 and above: Obese (Class II or III)
For Mounjaro eligibility, you need BMI 30 or above, or BMI 27–29.9 with a weight-related health condition. For South Asian, Chinese, Black African, or Black Caribbean adults, the overweight BMI threshold for Mounjaro is lower—eligibility may begin at BMI 27.5 or above. A prescriber will assess whether Mounjaro is appropriate for you based on your BMI, health conditions, and overall medical history.
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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.
BMI limitations and what else matters for Mounjaro
BMI has important limitations: it doesn't distinguish between muscle and fat, so athletes or very muscular individuals may have a high BMI without excess body fat. BMI also doesn't account for where fat is stored—waist circumference is equally important. The NHS recommends checking both BMI and waist measurement when assessing weight-related health risk. Men with a waist over 94cm (37in) and women over 80cm (31.5in) have increased health risk. Your GP will consider these factors alongside BMI when assessing Mounjaro eligibility, ensuring a personalised approach to your health.
- 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 get Mounjaro on the NHS if my BMI is 28?
If your BMI is 28 and you have a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea), you may be eligible. Your GP will assess this through NHS specialist weight management services. Without a qualifying condition, a BMI of 28 typically falls below the standard NHS threshold of 30 unless you're from South Asian or other ethnic minority backgrounds with lower qualifying thresholds.
How do I calculate my BMI for Mounjaro eligibility?
Divide your weight in kilograms by your height in metres squared. For example, at 75kg and 1.70m tall: 75 ÷ (1.70)² = 25.9 BMI. Use our free BMI calculator on this page to check instantly—it shows your BMI, category, and healthy weight range for your height according to NHS guidelines.
Do South Asian adults have different BMI thresholds for Mounjaro?
Yes. The NHS recognises that South Asian, Chinese, Black African, and Black Caribbean adults face higher cardiovascular and metabolic disease risk at lower BMI levels. Your BMI threshold for Mounjaro eligibility may start at 27.5 or above rather than 30. Speak to your GP about your specific ethnic background and qualifying BMI range.
What if I have a high BMI but no health conditions—am I eligible for Mounjaro?
If your BMI is 30 or above, you're generally eligible for Mounjaro in the UK regardless of other health conditions. However, a prescriber will still conduct a full clinical assessment to ensure the medication is safe and appropriate for you. Conditions like pregnancy, allergy to tirzepatide, or certain digestive issues may affect eligibility.
Is BMI the only thing that matters for Mounjaro eligibility?
No. While BMI is a key screening tool, prescribers also consider waist circumference, weight-related health conditions, medication history, kidney and liver function, and whether you're pregnant or breastfeeding. BMI is useful but has limitations—it doesn't account for muscle mass or fat distribution. Your GP will take a holistic view of your health before prescribing.
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.