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?
To be eligible for Mounjaro (tirzepatide) in the UK, you generally need a BMI of 30 or above, or a BMI between 27 and 29.9 if you have weight-related health conditions like type 2 diabetes, high blood pressure, or heart disease. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds due to higher health risks at these weights. Your GP or a licensed prescriber will assess your individual circumstances during a clinical consultation to determine whether this prescription-only medication is right for you.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Requirements and Eligibility Thresholds
The BMI formula used in the UK is weight (kg) ÷ height (m)². A healthy BMI according to NHS guidelines is between 18.5 and 24.9. For Mounjaro eligibility, you need to fall into different ranges depending on your circumstances:
- BMI 30 or above: Eligible for Mounjaro regardless of health conditions
- BMI 27–29.9: Eligible if you have weight-related health conditions (type 2 diabetes, prediabetes, hypertension, high cholesterol, sleep apnoea, or cardiovascular disease)
- Ethnicity adjustments: South Asian, Chinese, Black African, and Black Caribbean adults may be eligible from BMI 27.5 due to higher metabolic health risks at lower weights
Use our free BMI calculator above to check your personal BMI instantly. These bmi categories uk reflect current NHS guidance and may vary slightly depending on your local integrated care board.
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 Complementary Health Measures
BMI limitations are important to understand. BMI does not distinguish between muscle and fat — athletes or very muscular individuals may have a high BMI but low body fat percentage. BMI also ignores where fat is stored; waist circumference is another key indicator of health risk. Men with a waist above 94cm and women above 80cm face increased cardiovascular risk. Your GP may also consider your age, family history, blood pressure, cholesterol levels, and blood sugar control when assessing Mounjaro eligibility. A comprehensive health assessment is always more accurate than BMI alone for determining treatment suitability.
- 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 below 30?
Yes, if your BMI is between 27 and 29.9 and you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. NHS eligibility criteria also take into account ethnicity — lower thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults due to increased metabolic health risks.
What is the BMI range for overweight according to NHS guidelines?
The NHS defines the overweight BMI threshold as 25.0 to 29.9. A BMI below 25 is considered healthy weight. Use our free BMI calculator on this page to check where you fall and understand what your BMI means for your personal health.
Does BMI tell the whole story about whether I'm eligible for Mounjaro?
No. BMI is a useful screening tool, but your prescriber will also consider your medical history, current health conditions, waist circumference, blood pressure, and blood sugar levels. A clinical assessment is always more comprehensive than BMI alone when determining suitability for prescription weight loss treatment.
How do I calculate my BMI to check Mounjaro eligibility?
Use the BMI formula: weight in kg ÷ (height in metres)². For example, if you weigh 85kg and are 1.75m tall, your BMI is 85 ÷ (1.75)² = 27.8. Our free BMI calculator above does this instantly — just enter your weight and height in stone, pounds, or kilograms.
Are lower BMI thresholds for Mounjaro applied in the UK for certain ethnic groups?
Yes. The NHS recognises that South Asian, Chinese, Black African, and Black Caribbean individuals face higher risks of type 2 diabetes and cardiovascular disease at lower BMI levels. Eligibility thresholds may start from BMI 27.5 or lower for these groups, and your prescriber will discuss this during your clinical assessment.
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.