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
Can Metformin Help Weight Loss in the UK?
Metformin is a diabetes medication that may contribute to modest weight loss in some people, but it's not licensed for weight management in the UK. If you're looking for prescription weight loss medication, the NHS and private providers offer licensed alternatives specifically designed for weight management. This guide explains how metformin compares to approved options and how to find out if you're eligible for specialist weight loss support.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Weight Loss Medications Available
If you're seeking effective prescription weight loss medication in the UK, several licensed options are available through both NHS specialist services and private prescribing. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GLP-1 and GIP receptor agonist, helping regulate appetite and support feeling fuller after meals. Clinical trials showed participants lost an average of 15–21% of their body weight — though individual results vary significantly. Wegovy (semaglutide) is another once-weekly GLP-1 injection, with trial data showing approximately 15% average weight loss. Both are prescription-only medicines requiring a clinical assessment before being prescribed. Saxenda (liraglutide) is a daily GLP-1 injection option also licensed for weight management in UK adults. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses and understand how these medications might support your weight management goals.
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 Access and Eligibility
Access to prescription weight loss medication through the NHS requires referral to a tier 3 specialist weight management service — availability varies significantly by region and waiting lists can be lengthy. Eligibility typically includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Private prescription weight loss is available without NHS referral through online clinical assessments with UK-licensed prescribers. Your GP is the best starting point — they can discuss your suitability for treatment, refer you to NHS services if appropriate, or advise on private options. Calculate your BMI using our free BMI calculator to understand where you sit on NHS guidelines, and track your progress with our progress tracker once you begin any weight management journey.
- 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.
Does metformin cause weight loss?
Metformin may lead to modest weight loss in some people, typically 2–3 kg over several months. It's not licensed for weight management in the UK and works primarily by improving insulin sensitivity in people with type 2 diabetes. It's much less effective than licensed weight loss medications like Mounjaro or Wegovy.
What's the difference between metformin and Mounjaro for weight loss?
Metformin is a diabetes medication with incidental weight loss effects; Mounjaro is specifically licensed for weight management and uses a dual GLP-1/GIP mechanism. Clinical trials show Mounjaro users lose 15–21% of body weight on average, far exceeding metformin's modest effects. Only Mounjaro is prescribed specifically for weight loss in the UK.
Can I get Mounjaro or Wegovy on the NHS in the UK?
Yes, both Mounjaro and Wegovy are available through NHS tier 3 specialist weight management services. You'll need a GP referral and meet eligibility criteria (typically BMI ≥30, or ≥27 with weight-related health conditions). NHS availability and waiting times vary significantly by region. Private prescription is also available without NHS referral.
What does "prescription-only" mean for weight loss injections?
Prescription-only means these medications cannot be purchased without a valid prescription from a UK-licensed prescriber. A clinical assessment is required to check eligibility, review your medical history, and ensure the medication is safe for you. This applies to both NHS and private prescriptions.
How do I find out if I'm eligible for weight loss medication in the UK?
Start by calculating your BMI using a free BMI calculator to see where you stand relative to NHS guidelines (30 or above, or 27 with comorbidities). Then speak with your GP, who can assess your individual health and refer you to NHS specialist services or advise on private options. A licensed prescriber will conduct a full clinical assessment before prescribing.
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.