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
Will Metformin Help With Weight Loss?
Metformin is a diabetes medication that may support modest weight loss in some people, typically around 2–3 kg over several months. However, it's not licensed for weight management in the UK and results are variable. If you're interested in weight management through prescription medication, stronger options are available on the NHS and privately. This guide covers metformin's effects, alternatives, and how to find out if you're eligible for more effective weight loss medication 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.
UK-Licensed Weight Loss Medications
If you're looking for prescription weight loss medication in the UK, three options are currently licensed specifically for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that activates GLP-1 and GIP pathways. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection with average weight loss of around 15% in clinical trials.
- Saxenda (liraglutide) — a daily GLP-1 injection, though less commonly prescribed than Mounjaro and Wegovy.
All three are prescription-only and require a clinical assessment to determine eligibility. Unlike metformin, these medications are specifically designed for weight management and show significantly stronger evidence in clinical trials. Results vary between individuals, and all work best alongside a reduced-calorie diet and increased physical activity.
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.
Accessing Weight Loss Medication in the UK
You can access weight loss medication through two routes: the NHS or privately. On the NHS, you'll typically need a referral from your GP to a tier 3 specialist weight management service, though availability varies significantly by region and waiting times can be lengthy. Privately, you can access weight loss medication through GPhC-registered online prescribing services following an online clinical assessment — no NHS referral needed.
Eligibility generally 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. Your GP can advise on NHS options, or you can explore private assessment to find out if prescription weight loss medication is suitable for you. Use our free BMI calculator above to check your personal BMI and weight management 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.
Does metformin cause weight loss?
Metformin may support modest weight loss in some people, typically 2–3 kg over several months, particularly those with type 2 diabetes or prediabetes. However, weight loss is not assured and is usually modest. Metformin is approved for blood sugar management, not weight loss. Stronger options specifically licensed for weight management are available on prescription in the UK.
What's the difference between metformin and weight loss injections like Mounjaro?
Metformin is a tablet that primarily manages blood sugar and may incidentally support modest weight loss. Mounjaro and Wegovy are injections specifically designed for weight management with stronger clinical evidence — average weight loss of 15–21% body weight in trials. They work through different mechanisms (GLP-1 and GIP pathways) and produce more significant results for eligible adults.
Can I get Mounjaro or Wegovy on the NHS?
Yes, both Mounjaro and Wegovy are available on the NHS through specialist tier 3 weight management services. You'll need a GP referral and will be assessed for eligibility (typically BMI 30+, or 27+ with health conditions). Availability and waiting times vary significantly by region. Private access is faster and doesn't require an NHS referral.
How do I know if I'm eligible for weight loss medication in the UK?
Generally, you're eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess NHS eligibility, or you can use our free BMI calculator to check your current BMI and discuss options with a healthcare professional.
How quickly will I lose weight on prescription medication?
Weight loss varies significantly between individuals. In clinical trials, people taking Mounjaro lost an average of 15–21% of body weight over 72 weeks, and those taking Wegovy lost around 15%. Most weight loss occurs gradually over several months. The NHS recommends losing 0.5–1 kg per week for sustainable results. All weight loss medications work best alongside a reduced-calorie diet and increased physical activity, not as a substitute for lifestyle changes.
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.