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 Surgery vs Prescription Medication in the UK
If you're searching for weight loss surgery information, you may not realise that prescription weight management medication is now widely available in the UK for eligible adults. Unlike surgery, which carries surgical risks and requires lengthy NHS waiting lists or private costs, modern prescription options like Mounjaro and Wegovy work alongside lifestyle changes to support sustainable weight loss. This guide explains UK-licensed medication alternatives, how to find out if you're eligible, and how to start a conversation with your GP about the right option 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 Management Options
The UK has three prescription-only weight management medications licensed for adults with obesity or overweight conditions. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist administered once weekly, with clinical trials showing average weight loss of 15–21% of body weight. Wegovy (semaglutide) is a GLP-1 receptor agonist also injected once weekly, with trials demonstrating approximately 15% average weight loss. Saxenda (liraglutide) is a daily GLP-1 injection option.
Eligibility includes adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply due to higher health risks at lower weights. All three medications work best alongside reduced-calorie diet and increased physical activity. Try our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
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
NHS access is through tier 3 specialist weight management services, typically requiring GP referral. NHS availability varies significantly by region and waiting lists can be lengthy. Private access is through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, available without NHS referral, though costs apply (typically £129–£320 monthly depending on dose).
Start by speaking to your GP about weight management options. Your GP can assess whether prescription medication is suitable for you, refer you to NHS specialist services if eligible, or discuss private options. Use our free BMI calculator above to check your current BMI — this will help inform your conversation. Your prescriber will consider your individual health, medications, and goals before recommending the best approach 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.
Is prescription weight loss medication available on the NHS?
Yes. Mounjaro and Wegovy are approved for NHS use through specialist tier 3 weight management services. However, access varies by region and availability can be limited. Your GP can refer you if you meet eligibility criteria, though waiting lists may be lengthy in some areas.
How much weight can I expect to lose with medication like Mounjaro?
Clinical trials showed Mounjaro users lost an average of 15–21% of body weight over 72 weeks alongside diet and exercise. Individual results vary significantly. Some people lose more, some less. It works best as part of a complete lifestyle approach, not as a standalone treatment.
Do I need surgery if I'm eligible for prescription weight loss medication?
Not necessarily. Prescription medications offer a non-surgical alternative for many people. Surgery is typically considered when other methods haven't worked or for severe obesity with significant health complications. Discuss all options with your GP or specialist.
How do I know if I'm eligible for weight loss medication in the UK?
General eligibility includes BMI of 30 or above, or BMI of 27–29.9 with weight-related conditions. Lower thresholds apply for certain ethnic groups. Your GP or a licensed prescriber can assess your individual circumstances and determine suitability.
What's the difference between Mounjaro and Wegovy?
Mounjaro uses dual GIP and GLP-1 hormone pathways, while Wegovy uses GLP-1 alone. Mounjaro is injected weekly at doses up to 15mg; Wegovy is weekly up to 2.4mg. Clinical trial data suggests similar weight loss outcomes, though individual results vary. Your prescriber will recommend based on your health profile.
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.