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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Weight Loss Medication Options in the UK
If you're exploring weight management in the UK, prescription medication may be an option if you meet specific eligibility criteria. Private health providers like Bupa offer weight loss medication access alongside NHS services, though the route you take depends on your circumstances and BMI. This guide covers the prescription weight loss medications available, who's eligible, and how to find out if treatment is right for you.
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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.
UK-Licensed Weight Loss Medications & Eligibility
Three prescription-only medications are licensed in the UK for weight management: Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide), a GLP-1 receptor agonist; and Saxenda (liraglutide), also a GLP-1 agonist. To be eligible for prescription weight loss medication in the UK, you generally need a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease.
For adults of South Asian, Chinese, Black African, or Black Caribbean descent, the NHS recommends lower BMI thresholds, as these groups face higher health risks at lower weights. Clinical trials show significant average weight loss—Mounjaro users lost approximately 15–21% of their body weight, whilst Wegovy users averaged around 15%—though individual results vary considerably. These medications work alongside a reduced-calorie diet and increased physical activity, not as a replacement for lifestyle changes.
Clinically BackedWeight Loss
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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.
NHS vs Private Access for Weight Loss Medication
In the UK, you can access weight loss medication through two routes. NHS access is provided through specialist tier 3 and tier 4 weight management services, usually following a referral from your GP. Availability varies significantly by region, and waiting lists can be lengthy. Private access through providers and online pharmacies allows you to obtain a prescription without an NHS referral, provided a licensed UK prescriber assesses you as clinically suitable. Whether you choose NHS or private, a clinical assessment is essential—a healthcare professional will review your medical history, current medications, and BMI to determine if prescription medication is appropriate.
To find out if you're eligible, start by using our free BMI calculator to check your current BMI, then speak with your GP about your weight management goals and whether prescription medication might help you lose weight in the UK context.
- 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 is the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst Wegovy (semaglutide) activates the GLP-1 pathway only. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%). Both are once-weekly injections, prescription-only, and require clinical assessment before use. Individual results vary significantly.
How do I check if I'm eligible for prescription weight loss medication in the UK?
Generally, you're eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions. Use our BMI calculator to find your current BMI, then discuss your options with your GP. They can assess your individual circumstances and either refer you to NHS specialist services or discuss private options with you.
Can I get weight loss medication through Bupa or private insurance?
Private providers and online pharmacies can prescribe weight loss medication if a licensed UK prescriber assesses you as clinically suitable. Private access does not require an NHS referral. Costs and coverage vary by provider. Always ensure you're using a GPhC-registered pharmacy and a UK-licensed prescriber.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and around 15% with Wegovy over 1–2 years, alongside diet and exercise. However, individual results vary considerably—some people lose more, others less. Your GP can discuss realistic expectations during a clinical assessment.
What happens if I don't meet the BMI threshold for prescription medication?
If your BMI is below the threshold, lifestyle changes including diet, exercise, and behaviour support remain the most important approaches. The NHS recommends losing 0.5–1 kg per week through sustainable calorie deficit. Speak with your GP about weight management support available to you, or use our weight loss calculator to explore realistic weight loss projections. ```
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.