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
Metformin for Weight Loss in the UK
Metformin is primarily a type 2 diabetes medication, not licensed for weight loss in the UK. However, if you're looking for prescription weight management options, several UK-licensed medications are specifically designed for weight loss and may be available through the NHS or private prescribing. This guide explains what's actually available for weight management in the UK, how eligibility works, and how to find out if you qualify for prescription support.
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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.
UK-Licensed Prescription Weight Loss Medications
While metformin isn't approved for weight loss in the UK, several prescription-only medications are specifically licensed for weight management. These include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide)—all GLP-1 or dual GIP/GLP-1 receptor agonists that help regulate appetite and support weight loss alongside diet and exercise.
Clinical trials show these medications may help adults lose an average of 15–21% of body weight, though individual results vary significantly. Mounjaro is a once-weekly injection with a dual mechanism, while Wegovy is a once-weekly GLP-1 injection. Eligibility for prescription weight loss medication in the UK typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. You can check your personal BMI using our free BMI calculator above to see where you stand.
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.
NHS vs Private Weight Loss Medication in the UK
NHS access: Prescription weight loss medications are available through NHS tier 3 specialist weight management services, though access varies significantly by region and waiting lists can be lengthy. Your GP can refer you to your local specialist service if you meet the eligibility criteria.
Private access: Weight loss injections are also available through UK-registered online pharmacies following an online clinical assessment with a licensed prescriber. This route does not require an NHS referral and can be faster, though there is a cost involved. Either way, a prescriber will assess your individual health circumstances before issuing a prescription. If you're unsure about your eligibility, start a conversation with your GP or explore a private clinical assessment to understand your options.
Use our free GLP-1 weight loss calculator to explore potential weight loss outcomes at different doses, and our weight converter to track progress in familiar measurements. The progress tracker tool can help you log your weight loss journey over time if you choose to start treatment. Remember, sustainable weight loss combines prescription support with reduced-calorie diet and increased physical activity—medication is most effective as part of a comprehensive approach.
- 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.
Is metformin prescribed for weight loss in the UK?
No. Metformin is licensed only for type 2 diabetes management in the UK, not for weight loss. However, some people with diabetes may experience modest weight loss as a side effect. For licensed weight loss medications, your GP or prescriber would consider Mounjaro, Wegovy, or Saxenda instead, which are specifically approved for weight management.
What's the difference between metformin and GLP-1 weight loss medications?
Metformin is an insulin-sensitising diabetes drug with limited weight loss evidence. GLP-1 medications like Wegovy and Mounjaro work by activating appetite-regulating hormones and are licensed specifically for weight management. Clinical trials show significantly greater weight loss with GLP-1 medications—typically 15–21% of body weight compared to minimal loss with metformin alone.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Check your BMI using our free calculator above, then speak with your GP or a licensed prescriber who can assess your individual circumstances and medical history.
Can I get weight loss injections through the NHS in the UK?
Yes, prescription weight loss medications are available through NHS specialist tier 3 weight management services. However, access varies by region and waiting lists can be substantial. Your GP can refer you if you meet eligibility criteria. Private prescribing is also available as a faster alternative with associated costs.
What should I do if I want to explore weight loss medication options?
Start by calculating your BMI using our free tool above. Then contact your GP to discuss referral to specialist weight management services, or explore a private clinical assessment with a UK-registered prescriber. Either route will involve a consultation to assess whether prescription medication is appropriate for your health and weight loss goals.
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.