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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Best Supplement For Weight Loss in the UK
If you're searching for the best supplement for weight loss, it's worth knowing that the most effective options available in the UK are actually prescription medications, not over-the-counter supplements. These are licensed weight management injections backed by clinical evidence. This guide explains what prescription weight loss medication is available in the UK, who may be eligible, and how to discuss your options with your GP. Use our free BMI calculator above to check your starting point and explore whether prescription weight loss support might be right for you.
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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
The most evidence-backed weight loss options available in the UK are prescription-only medications, not supplements. Three main options are licensed for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist injection. Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks, with results varying by dose and individual response.
- Wegovy (semaglutide) — a GLP-1 receptor agonist injection. The STEP-1 trial showed average weight loss of approximately 15% of body weight at the maximum dose.
- Saxenda (liraglutide) — also a GLP-1 agonist, but given as a once-daily injection rather than weekly. Average weight loss is typically 5–10% of body weight.
All three require a prescription and clinical assessment. They work by reducing appetite, helping you feel fuller, and supporting better control over food choices. Results vary significantly between individuals and are most effective 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.
Eligibility and How to Access Weight Loss Medication in the UK
To be eligible for prescription weight loss medication in the UK, you typically need a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds due to higher health risks at lower weights.
You can access weight loss medication through the NHS via referral to a specialist tier 3 weight management service, though waiting lists vary by region. Alternatively, private online prescribing services offer faster access following a clinical assessment by a UK-licensed prescriber. Either route requires your prescriber to assess that medication is appropriate for your individual health. Start by speaking with your GP about your weight management goals and whether prescription options might be suitable for you.
- 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.
Are weight loss supplements available over the counter in the UK better than prescription options?
Most over-the-counter weight loss supplements have limited clinical evidence compared to prescription medications like Mounjaro and Wegovy. Prescription options are licensed based on robust clinical trials demonstrating measurable weight loss. Always check with your GP before starting any supplement or medication.
How much weight can I expect to lose with prescription weight loss medication?
Results vary significantly between individuals. Clinical trials show average weight loss of 15–21% for Mounjaro and around 15% for Wegovy, but individual outcomes depend on factors like starting weight, adherence, diet, and physical activity. Individual results vary considerably.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Mounjaro showed slightly higher average weight loss in trials (up to 21% vs 15%), but both are effective. Your prescriber will assess which is more suitable based on your health profile.
Can I get weight loss medication on the NHS?
Yes. NICE has approved Mounjaro and other weight loss medications for use through NHS specialist weight management services (tier 3). However, access varies significantly by region and waiting lists can be lengthy. Your GP can refer you to check local availability.
How do I know if I'm eligible for prescription weight loss medication?
You can use our free BMI calculator above to check your starting BMI. Generally, adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may be eligible. Speak with your GP or a licensed prescriber who can assess your individual circumstances and eligibility.
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.