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 Medication in the UK — What You Need to Know
If you're looking for weight management support in the UK, prescription medication may be an option. NICE guidelines outline which treatments are available on the NHS and privately, and who may be eligible. This guide covers the main prescription weight loss options available to UK adults, how they work, and how to find out if you might qualify for treatment through 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 main prescription weight loss medications are licensed in the UK for weight management in adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, while Saxenda is a daily injection. Each works differently but shares similar goals — helping reduce appetite and supporting sustainable weight loss alongside diet and physical activity changes.
Clinical trials show these medications can help patients lose an average of 15–21% of their body weight over several months, though individual results vary significantly. To be eligible, you typically need a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or heart disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds due to increased health risks at those weights.
Our free GLP-1 weight loss calculator can help you understand potential outcomes at different doses, and our BMI calculator will show you where your current weight sits relative to these eligibility thresholds.
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 — How to Get Started
In the UK, prescription weight loss medication is available through two routes: NHS specialist weight management services or private online prescribing from a UK-licensed prescriber. NHS access requires referral from your GP to a tier 3 or tier 4 specialist service — availability varies by region, and waiting lists can be lengthy in many areas. Private access is available without an NHS referral through GPhC-registered online pharmacies, typically following a brief online clinical assessment.
To explore your options, start by speaking with your GP about your weight management goals. They can assess whether medication might be suitable for you, discuss NHS availability in your area, and help you understand any health conditions that might affect eligibility. Your GP can also check for any interactions with medicines you're already taking.
- 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.
What is the NICE guidance on weight loss medication?
NICE recommends that prescription weight loss medications (Mounjaro, Wegovy, and Saxenda) should be offered to adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, as part of a comprehensive weight management programme. Medications should be used alongside reduced-calorie diet and increased physical activity, not as a replacement for lifestyle changes.
Am I eligible for weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related condition like type 2 diabetes or high blood pressure. Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Ask your GP to refer you to a specialist weight management service to check your individual eligibility.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight over several months, but individual results vary considerably. Some people lose more, some less. Weight loss depends on the medication, dose, adherence, and how well you follow dietary and activity changes alongside treatment.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but both are effective. Your prescriber will help determine which is most suitable for you.
Can I get weight loss medication privately if I'm not eligible on the NHS?
Yes. Private online prescribing is available through UK-licensed prescribers who assess you via an online consultation. If you don't meet NHS criteria or prefer not to wait for NHS services, private prescription is an option — though you'll pay for the medication privately. Costs vary depending on dose and provider.
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.