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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NHS Requirements for Mounjaro and Wegovy — What You Need to Know
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management medications available through NHS specialist services in the UK, though eligibility and NHS access vary significantly by region. This guide explains the clinical requirements, BMI thresholds, and how NHS criteria compare between these two GLP-1 and dual GIP+GLP-1 medications. Whether you're eligible depends on your BMI, health conditions, and local NHS availability — your GP can advise on access in your area.
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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 and BMI Thresholds for Both Medications
The NHS NICE guidelines approve both Mounjaro and Wegovy for weight management in UK adults meeting specific criteria. Standard eligibility requires either a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² alongside at least one weight-related health condition.
- Weight-related health conditions that may qualify: type 2 diabetes or prediabetes, high blood pressure (hypertension), abnormal blood fats (dyslipidaemia), obstructive sleep apnoea, or history of cardiovascular disease (heart attack or stroke)
- For South Asian, Chinese, Black African, or Black Caribbean adults: lower BMI thresholds apply — eligibility may begin at BMI 27.5 or above, because these groups face higher cardiovascular and metabolic risk at lower weights
- Age requirement: 18 years and over
- Clinical assessment requirement: both medications require a full clinical assessment before prescription
Use our free BMI calculator to check your personal BMI instantly and understand where you fall within these NHS thresholds.
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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.
Clinical Trial Data and Individual Prescriber Decision-Making
Mounjaro and Wegovy have different mechanisms and clinical trial results. SURMOUNT-1 trials showed Mounjaro (a dual GIP+GLP-1 agonist) resulted in average weight loss of approximately 15–21% of body weight, while STEP-1 trials showed Wegovy (GLP-1 agonist only) achieved average weight loss of around 14.9%. However, individual results vary significantly. A prescriber will assess which medication is more suitable for your personal health profile, medical history, and circumstances. NHS specialist weight management services consider factors including previous medications tried, side effect tolerance, and presence of type 2 diabetes — because Mounjaro's dual action may offer additional metabolic benefits for diabetic patients.
- 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 BMI do I need to access Mounjaro or Wegovy through the NHS?
You generally need a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease). If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply — consult your GP for your personal eligibility. Our BMI calculator can help you determine your current BMI status.
What's the difference between Mounjaro and Wegovy in terms of NHS access?
Both medications are approved by NICE and available through NHS tier 3 specialist weight management services. Mounjaro is a dual GIP+GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Availability varies by region and local NHS service capacity. Your GP can refer you to your local specialist service, but waiting times may be significant in some areas.
Can I get Mounjaro or Wegovy on NHS prescription from my GP directly?
Generally, no — both medications are typically prescribed through specialist tier 3 or tier 4 NHS weight management services rather than standard GP prescriptions. Your GP can refer you to the specialist service in your local area, but they cannot usually prescribe these medications themselves. Regional availability and waiting lists vary considerably.
What weight-related health conditions make me eligible for these medications?
Qualifying conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal blood cholesterol levels, obstructive sleep apnoea, or a history of heart attack or stroke. If you have any of these alongside overweight (BMI 27–29.9) or obesity (BMI 30+), you may be eligible. Discuss your personal medical history with your GP to understand your suitability.
How long does it take to get Mounjaro or Wegovy through the NHS?
NHS waiting times vary significantly by region and local service capacity. In some areas, waiting lists for tier 3 specialist services extend several months or longer. Private online prescribing offers faster access but involves payment. Speak to your GP about current waiting times in your local NHS integrated care board area.
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.