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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Who Qualifies for Mounjaro in the UK?
If you're considering Mounjaro (tirzepatide) for weight management in the UK, you'll need to meet specific eligibility requirements based on your BMI and health profile. Mounjaro is a prescription-only medication, and whether you can access it depends on your weight, any weight-related health conditions, and your ethnic background. This guide explains exactly what you need to qualify and how the process works in the UK.
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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.
BMI Thresholds and Eligibility
Mounjaro eligibility in the UK is primarily based on BMI, though other factors apply. You may be eligible if:
- Your BMI is 30 kg/m² or above (obese category), OR
- Your BMI is 27–29.9 kg/m² (overweight) AND you have at least one weight-related health condition
If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — you may qualify at a BMI of 27.5 or above, as these populations face higher health risks at lower BMI levels.
Use our free BMI calculator above to check your current BMI instantly, then compare it against these thresholds. Your GP or prescriber will also assess your weight using our weight converter to ensure accurate measurements in both metric and imperial units.
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.
Health Conditions and Other Requirements
Even if your BMI is below 30, you may qualify if you have one or more weight-related health conditions. These include type 2 diabetes, prediabetes, high blood pressure (hypertension), abnormal cholesterol levels, obstructive sleep apnoea, or a history of heart attack or stroke.
You cannot take Mounjaro if you're under 18, pregnant, planning pregnancy, breastfeeding, or allergic to tirzepatide. Your prescriber will assess your full medical history, current medications (particularly oral contraceptives and diabetes treatments), and any contraindications. Access routes vary: NHS specialist weight management services (tier 3) may prescribe Mounjaro following referral, though availability and waiting times vary by region. Private prescribing via UK-licensed online providers is also available without NHS referral.
- 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 requirement for Mounjaro in the UK?
You need a BMI of 30 or above, or 27–29.9 with a weight-related health condition like type 2 diabetes, high blood pressure, or sleep apnoea. South Asian and Black African/Caribbean adults qualify at BMI 27.5+ due to higher health risks at lower weights.
Do I need to be referred to the NHS to get Mounjaro?
For NHS access, you typically need referral to a specialist tier 3 weight management service through your GP. Private UK-licensed prescribers also offer Mounjaro via online assessment without NHS referral. Availability and waiting times vary significantly by region.
Can I take Mounjaro if I'm taking oral contraceptives?
Mounjaro may reduce how your body absorbs oral contraceptives. If you use the pill, your prescriber will advise adding a barrier method or switching to a different contraceptive for 4 weeks after starting and after each dose increase.
What happens at my Mounjaro assessment?
Your prescriber will check your BMI, medical history, current medications, and weight-related health conditions. They'll confirm you meet eligibility criteria, discuss how tirzepatide works, and review potential side effects before issuing a prescription if appropriate.
Is Mounjaro the same as Ozempic or Wegovy?
No. Mounjaro contains tirzepatide (a dual GIP+GLP-1 agonist), while Wegovy contains semaglutide (GLP-1 only). Ozempic also contains semaglutide but is licensed for diabetes, not weight loss. All three are prescription-only and 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.