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 to Get Mounjaro in the UK?
To be eligible for Mounjaro (tirzepatide) in the UK, you 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 heart disease. If you're from a South Asian, Chinese, Black African, or Black Caribbean background, slightly lower thresholds may apply due to higher health risks at lower BMI levels. Your prescriber will assess your individual circumstances, but understanding your personal BMI is the crucial first step.
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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.
Mounjaro BMI Eligibility Thresholds in the UK
Mounjaro is approved in the UK for adults meeting these BMI eligibility criteria:
- BMI of 30 or above (obesity classification) — eligible regardless of health conditions
- BMI of 27–29.9 (overweight) — eligible if you have at least one weight-related health condition
Weight-related conditions that may qualify include type 2 diabetes, prediabetes, high blood pressure (hypertension), abnormal blood fats (dyslipidaemia), obstructive sleep apnoea, or a history of cardiovascular disease.
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds: eligibility may start at BMI 27.5 or above due to increased health risks at lower BMI levels within these populations. Calculate your personal BMI using our free BMI calculator to see where you fall.
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.
BMI Limitations and What Else Matters
While BMI is a useful screening tool, it has important limitations. BMI does not distinguish between muscle and fat — athletes or very muscular individuals may have a high BMI but low body fat. BMI also does not account for where fat is stored; waist circumference is equally important for assessing health risk. Your GP will consider BMI alongside other factors like blood pressure, blood sugar levels, cholesterol, and your personal health history when assessing whether Mounjaro is right for you. Using our free weight converter and BMI calculator together gives you a complete picture before your consultation.
- 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 exact BMI number do I need for Mounjaro?
You need a BMI of 30 or above for automatic eligibility, or 27–29.9 if you have weight-related health conditions. For South Asian or Black African backgrounds, lower thresholds apply. Your prescriber assesses individual circumstances — BMI alone doesn't determine eligibility. Use our BMI calculator to find your exact BMI and discuss it with your GP or healthcare provider.
Is BMI the only factor prescribers consider?
No. Prescribers also assess your overall health, medical history, current medications, waist circumference, blood pressure, and blood sugar levels. BMI is a useful screening tool but has limitations — it doesn't account for muscle mass or fat distribution. Your individual health needs guide the decision.
Can I get Mounjaro on the NHS with my BMI?
NHS access to Mounjaro depends on your BMI, health conditions, and your region's ICB availability. You'll need referral to a tier 3 specialist weight management service from your GP. Waiting times vary significantly by area. Private prescribing is available without NHS referral if you meet eligibility criteria.
What if my BMI is just under 30 but I have health conditions?
If your BMI is 27–29.9 and you have weight-related conditions like type 2 diabetes, high blood pressure, or heart disease, you may be eligible for Mounjaro. Your prescriber will assess whether your specific health circumstances support treatment. Always discuss your individual case with your GP.
How do I calculate my BMI accurately?
BMI is calculated as weight (kg) divided by height (m) squared. For example, at 1.73m tall, a weight of 85kg gives a BMI of about 28.4. Use our free BMI calculator on this page to get your exact BMI instantly, then use our weight converter to understand your weight in stone and pounds too.
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.