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
Who Qualifies for Mounjaro vs Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but eligibility criteria are identical for both medications. You may qualify if you have a BMI of 30 kg/m² or above, or a BMI of 27 to 29.9 kg/m² with at least one weight-related health condition. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply. Your GP or a licensed prescriber will assess your eligibility following a clinical evaluation. MyWeightCheck's free weight loss calculator can help you explore your BMI context before consulting your healthcare provider.
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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.
Standard NHS Eligibility Criteria
Both Mounjaro and Wegovy follow the same UK eligibility framework:
- BMI of 30 kg/m² or above (obesity classification), 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 cholesterol levels, obstructive sleep apnoea, and cardiovascular disease history. NHS NICE guidance aligns these criteria for both medications. However, ethnicity-adjusted thresholds apply: if you're of South Asian, Chinese, Black African, or Black Caribbean descent, you may qualify from BMI 27.5 kg/m² or above due to higher health risk at lower weights. A mounjaro kwikpen or Wegovy pen is only prescribed after a prescriber confirms you meet these criteria through a formal clinical assessment.
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.
Key Differences in Access Pathways
Although eligibility criteria are the same, access routes differ. NHS access requires referral to a specialist tier 3 or tier 4 weight management service — your GP refers you, though waiting times vary by region. Private access is available through UK-registered online prescribers without NHS referral. Both require a mounjaro uk prescription or Wegovy prescription from a licensed practitioner. Dose titration (starting low and increasing weekly) is identical for both: Mounjaro starts at 2.5 mg weekly up to 15 mg; Wegovy starts at 0.25 mg weekly up to 2.4 mg. Whichever medication you're prescribed, side effects are similar — nausea, constipation, and injection site reactions are common initially. Your prescriber will discuss which medication suits you best based on your health history.
- 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 in who qualifies for Mounjaro vs Wegovy?
There is no difference — both medications have identical NHS eligibility criteria. You qualify based on the same BMI thresholds (30+ or 27–29.9 with comorbidities). The choice between them depends on clinical assessment, personal preference, and prescriber recommendation, not eligibility status.
Do ethnicity-adjusted thresholds apply to both medications equally?
Yes. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, both Mounjaro and Wegovy may be prescribed from a BMI of 27.5 kg/m² onwards due to higher cardiovascular and metabolic risk in these populations. This is NHS guidance applicable to both medications.
Can I access Mounjaro or Wegovy through the NHS, or only privately?
Both are available through NHS specialist weight management services (tier 3/4), though access and waiting times vary significantly by region. Both are also available privately through UK-licensed prescribers without NHS referral, though there is a cost. Your GP can refer you to NHS services, or you can pursue private assessment independently.
If I don't qualify now, could I qualify later?
Yes. If your BMI changes, or if you develop a weight-related health condition (such as type 2 diabetes or high blood pressure), you may become eligible even if your BMI is between 27 and 29.9. Revisit eligibility with your GP or prescriber if your circumstances change.
Is the dose titration schedule the same for Mounjaro and Wegovy if I'm prescribed either one?
No — Mounjaro and Wegovy have different titration schedules. Mounjaro starts at 2.5 mg and increases weekly to a maximum of 15 mg. Wegovy starts at 0.25 mg and increases weekly to 2.4 mg. Your prescriber will explain your specific schedule once you're prescribed.
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.