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
What BMI Do You Need for Mounjaro in the UK?
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK for adults with specific BMI thresholds. Generally, you may be eligible if your BMI is 30 or above, or between 27 and 29.9 if you have weight-related health conditions. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. Your GP or a licensed prescriber will assess your individual eligibility following a clinical assessment. Use our free BMI calculator above to check your current 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 Thresholds for Mounjaro in the UK
According to NHS guidance, the BMI eligibility thresholds for Mounjaro are:
- BMI 30 or above — adults with obesity may be eligible regardless of other factors
- BMI 27 to 29.9 — adults classified as overweight with at least one weight-related health condition
Weight-related conditions that may qualify include type 2 diabetes, prediabetes, high blood pressure (hypertension), abnormal blood cholesterol (dyslipidaemia), obstructive sleep apnoea, or a history of cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean backgrounds, the NHS recommends lower thresholds: BMI 27.5 or above may qualify. The healthy BMI range uk standard is 18.5 to 24.9 for most adults. Calculate your exact BMI using our free BMI calculator on this page to see where you fall within these ranges.
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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.
BMI Limitations and Other Health Factors
While BMI categories uk are useful screening tools, BMI has important limitations — it does not distinguish between muscle and fat, so athletes or people with significant muscle mass may have a high BMI despite low body fat. Where you store fat also matters: waist circumference is an important indicator of health risk. The NHS recommends checking both your BMI and your waist measurement. Men with waist circumference over 94 cm (37 inches) or women over 80 cm (31.5 inches) face increased health risks. Your GP will consider your BMI alongside other health factors, medical history, and whether lifestyle changes alone have been unsuccessful before discussing prescription treatment options.
- 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 between 27 and 29.9?
Yes, potentially. If your BMI falls in this range and you have at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea), you may be eligible. However, NHS access varies by region, and you'll need a referral to a specialist weight management service. Waiting lists can be lengthy in many areas.
What is the exact BMI formula used for eligibility assessment?
The BMI formula is: weight (kg) ÷ height (metres) squared. For example, someone weighing 85 kg with a height of 1.75 m would have a BMI of 27.8. Use our free BMI calculator above to work out your exact figure instantly without a UK pharmacy calculation.
Do South Asian adults have different Mounjaro eligibility?
Yes. The NHS recognises that adults of South Asian, Chinese, Black African, and Black Caribbean heritage face higher health risks at lower BMI levels. For these populations, BMI thresholds start at 27.5 (rather than 30) for obesity, meaning eligibility for prescription weight loss treatment may begin earlier.
Will my GP automatically prescribe Mounjaro if my BMI meets the threshold?
No. Meeting the BMI threshold is necessary but not sufficient. Your prescriber will assess your overall health, medical history, any other medications, contraindications, and whether you've tried lifestyle changes first. Mounjaro is prescription-only and requires individual clinical assessment.
What should I do if my BMI is slightly below the threshold?
If your BMI is 27–29.9 without qualifying health conditions, discuss this with your GP. They may recommend lifestyle interventions first, or refer you to NHS tier 2–3 weight management services. Some private prescribers may assess individual cases differently, so clinical assessment is key.
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.