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 Have To Be For Mounjaro?
In the UK, you may be eligible for Mounjaro (tirzepatide) if your BMI is 30 or above, or 27 to 29.9 if you have weight-related health conditions. However, BMI is just one factor — your GP or a specialist will assess your individual health needs before prescribing. This guide explains the NHS eligibility criteria, how BMI thresholds work, and what happens next if you think you might qualify for this prescription weight loss medication.
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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 Requirements and Eligibility Criteria
Primary NHS eligibility threshold:
- BMI of 30 kg/m² or above (obese category), OR
- BMI of 27 to 29.9 kg/m² (overweight) with at least one weight-related health condition
Check your BMI using our free BMI calculator on this page to see where you fall.
Weight-related health conditions that may qualify: type 2 diabetes or prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or history of heart attack or stroke.
Special note for South Asian, Chinese, Black African, and Black Caribbean adults: The NHS applies lower BMI thresholds for these groups because they face higher health risks at lower weight. Eligibility may start at BMI 27.5 or above, even without additional health conditions. This follows NHS bmi range uk guidance that recognises ethnic health disparities.
Mounjaro is prescription-only and requires a clinical assessment before being prescribed. Your GP cannot simply prescribe it — you'll need referral to a specialist tier 3 weight management service in most cases.
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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.
The NHS Weight Management Pathway and How to Access Mounjaro
The NHS offers four tiers of weight management support. Mounjaro access typically happens at tier 3 (specialist services). First, speak to your GP about your weight concerns — they can assess your healthy bmi range and offer initial support through tier 1 or 2 services. If appropriate, your GP may refer you to a specialist weight management clinic. Availability and waiting times vary significantly by region — some areas have shorter waits than others.
Use our GLP-1 weight loss calculator to explore potential outcomes if you do become eligible. Remember that medication works alongside lifestyle changes like reduced-calorie diet and increased activity. Your bmi limitations also matter — BMI doesn't distinguish muscle from fat, so your GP will consider your full health picture, not just your number.
- 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's the exact BMI you need for Mounjaro on the NHS?
The main threshold is BMI 30 or above. If your BMI is 27–29.9, you may still qualify if you have weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For South Asian and some other ethnic groups, thresholds are lower (from 27.5). Use our BMI calculator to check yours.
Can I get Mounjaro through the NHS?
Yes, Mounjaro is approved by NICE for NHS use, but access is through specialist tier 3 weight management services. You'll need a GP referral. Waiting times vary by region — some areas have long lists. Many people access it privately through online prescribing instead.
What if my BMI is just below 30 — can I still get Mounjaro?
If your BMI is 27–29.9 and you have a qualifying health condition (diabetes, high blood pressure, sleep apnoea, heart disease history), you may be eligible. Speak to your GP about your specific situation. They can assess whether treatment is appropriate for you.
How does the NHS assess weight management needs beyond BMI?
The NHS uses a holistic approach. Doctors consider your BMI, weight-related health conditions, lifestyle, previous weight loss attempts, and whether you're motivated for change. BMI is a screening tool — your GP looks at your whole health picture, not just the number.
What's the difference between NHS and private Mounjaro access?
NHS access is through specialist services (tier 3) with a GP referral — typically free but with waiting lists. Private access is through online prescribing with a UK-licensed prescriber, available without NHS referral, but you pay for the medication. Both require 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.