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 Pills That Work in the UK
If you're searching for weight loss pills that work, prescription medication options are available in the UK for eligible adults. Mounjaro, Wegovy, and Saxenda are licensed prescription medicines designed to support weight management alongside diet and exercise. These medications work differently than over-the-counter supplements—they're prescription-only and require a clinical assessment. This guide explains what's available, how they work, who can access them, and whether the NHS or private routes suit your situation. Understanding your options helps you have an informed conversation with your GP.
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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 Options
Three prescription medications are currently licensed in the UK for weight management. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and food cravings. Clinical trials showed participants lost an average of 15–21% of their body weight—though individual results vary significantly. Wegovy (semaglutide) is also a once-weekly injection, working as a GLP-1 receptor agonist, with average weight loss around 15% in clinical trials. Saxenda (liraglutide) is a daily injection offering similar GLP-1 support.
All three are prescription-only medicines. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. Your prescriber will assess your suitability based on your medical history. Results always vary—these are population averages, not assured outcomes. Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses, and our BMI calculator to check your starting point.
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 in the UK
NHS access: Weight loss medication is available through NHS specialist tier 3 weight management services. You'll need a referral from your GP, and access varies by region—waiting lists can be lengthy. NICE has approved tirzepatide (Mounjaro) for eligible adults in NHS services.
Private access: Available through GPhC-registered online pharmacies following an online clinical assessment. You don't need an NHS referral, and prescriptions are issued if clinically appropriate. Costs range from approximately £129–£320 per month depending on dose and provider.
Start by asking your GP whether you're eligible for NHS weight management services or prescription medication. They can discuss your options, check your BMI using our weight converter tool if needed, and advise on the best route 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.
Do weight loss pills really work?
Prescription weight loss medications have strong clinical evidence. In trials, Mounjaro helped participants lose 15–21% of body weight, and Wegovy around 15%, alongside diet and exercise. Results vary between individuals. These are not supplements—they're prescription-only medicines that work by regulating appetite and metabolism.
How do I know if I'm eligible for weight loss pills in the UK?
You may be eligible if your BMI is 30 or above, or 27–29.9 with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Your GP can assess your individual eligibility.
Can I get weight loss pills on the NHS?
Yes, through NHS tier 3 specialist weight management services. You'll need a GP referral and assessment. Availability and waiting times vary significantly by region. Many areas have long waiting lists. Private options are also available if NHS waiting times are a concern.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trial data suggests slightly higher average weight loss with Mounjaro, but individual results vary. Your prescriber will recommend the most suitable option for you.
Are weight loss pills safe, and what are the side effects?
Prescription weight loss medications are safe for eligible adults when prescribed by a licensed prescriber. Common side effects include nausea, diarrhoea, and constipation—usually mild and temporary. Serious side effects are rare. Your prescriber will discuss all risks and benefits during your 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.