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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Mounjaro NHS Criteria UK — What You Need to Know
If you're considering Mounjaro for weight management in the UK, understanding NHS eligibility criteria is essential. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available through NHS specialist services and private prescribing routes. This guide explains the NHS criteria for both medications, how they compare, and what happens next if you're eligible. Use our free BMI calculator above to check your starting point before exploring your options.
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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.
NHS Eligibility Criteria for Mounjaro vs Wegovy
Both Mounjaro and Wegovy have identical NHS eligibility criteria:
- BMI of 30 kg/m² or above (obesity), or
- BMI of 27–29.9 kg/m² (overweight) with at least one weight-related health condition
Weight-related conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or history of cardiovascular disease.
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply: BMI 27.5 or above may qualify for treatment, reflecting higher cardiovascular risk at lower weights.
NHS access requires referral to a specialist tier 3 or tier 4 weight management service through your GP — not standard GP prescription. Regional availability varies significantly, and waiting lists can be lengthy in many areas. Both medications are prescription-only and require clinical assessment by a qualified prescriber.
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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.
Key Differences: SURMOUNT vs STEP Trial Results
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. In the SURMOUNT-1 clinical trial, participants on the 15 mg dose lost approximately 20.9% of their body weight over 72 weeks alongside diet and activity changes.
Wegovy (semaglutide) is a GLP-1-only receptor agonist. In the STEP-1 clinical trial, participants on the 2.4 mg dose lost approximately 14.9% of body weight over 68 weeks with similar lifestyle support.
Both medications are used as part of a comprehensive approach — not as standalone solutions. Individual results vary significantly. Your prescriber will assess which medication suits your circumstances, medical history, and personal health goals. Neither assures specific weight loss outcomes.
- 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 main difference between Mounjaro and Wegovy mechanisms?
Mounjaro activates both GIP and GLP-1 hormone pathways (dual action), while Wegovy activates GLP-1 only. This dual mechanism in Mounjaro may contribute to different appetite and metabolic effects, though both help reduce hunger and support feeling fuller after meals.
Can I access Mounjaro or Wegovy through the NHS immediately?
No. Both require referral to specialist weight management services (tier 3/4) through your GP. NHS eligibility is based on BMI thresholds and health conditions. Waiting times vary by region (ICB) and can range from weeks to many months in some areas.
What if my BMI is below 30 but I have health conditions?
You may still qualify if your BMI is 27–29.9 and you have weight-related health conditions such as type 2 diabetes, prediabetes, high blood pressure, or sleep apnoea. For certain ethnic groups, eligibility may start at BMI 27.5. Your GP can assess your individual circumstances.
How do Mounjaro and Wegovy doses compare?
Mounjaro ranges from 2.5 mg to 15 mg once weekly. Wegovy ranges from 0.25 mg to 2.4 mg once weekly. Approximate equivalences exist (Mounjaro 10 mg ≈ Wegovy 1.7 mg), but any switch between medications must be managed by your prescriber — there is no standard conversion protocol.
Can I use the NHS calculator to check my weight loss potential?
Yes. Try our free GLP-1 weight loss calculator above to estimate potential weight loss at different medication doses. This can help you understand typical outcomes, though individual results vary. Always discuss expectations with your prescriber during 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.