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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NHS Weight Loss Injection: UK Prescription Options Explained
Weight loss injections are now available through the NHS for eligible adults in the UK. These prescription medications can support weight management alongside diet and exercise when other methods haven't been effective. The main options include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Access varies by region, and you'll need to discuss eligibility with your GP or a specialist weight management service. This guide explains how NHS weight management injections work, who can access them, and what to expect.
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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 Injections & Clinical Evidence
Three prescription weight management injections are currently licensed in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that may help reduce appetite and support feeling fuller after meals. Clinical trials showed adults lost an average of 15–21% of body weight over 72 weeks. Wegovy (semaglutide) is a GLP-1 receptor agonist with similar effects, with clinical trials showing approximately 15% average weight loss. Saxenda (liraglutide) is a daily GLP-1 injection with slightly different dosing.
Eligibility criteria for prescription weight loss treatment in the UK include: BMI of 30 kg/m² or above, or BMI of 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may have access at lower BMI thresholds due to increased health risks. Use our BMI calculator above to check your personal BMI and understand how you measure against NHS guidelines.
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 Access vs Private: How to Get Started
NHS weight loss injections are accessed through specialist tier 3 weight management services, typically via referral from your GP. Availability varies significantly by region and local Integrated Care Boards (ICBs). Waiting lists for NHS specialist services can be lengthy in many areas, sometimes several months or longer depending on your location. Your GP can advise whether you meet local eligibility criteria and refer you if appropriate. Alternatively, private prescribing is available through GPhC-registered online pharmacies following a clinical assessment. To start, book an appointment with your GP to discuss your weight management goals and whether prescription medication might be suitable for you based on your individual health circumstances.
- 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 difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1-only medication. Clinical trials showed Mounjaro produced slightly higher average weight loss (15–21% vs 15%), but both are effective. Results vary between individuals, and suitability depends on personal health factors that a prescriber will assess.
How do I know if I'm eligible for NHS weight loss injections?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Lower BMI thresholds apply for certain ethnic backgrounds. Your GP can assess your eligibility and discuss whether referral to a specialist service is appropriate.
How long does it take to get NHS weight loss injection treatment?
Waiting times vary significantly by region. Some areas offer relatively quick access, while others may have waiting lists of several months. Contact your local NHS weight management service or ask your GP about current waiting times in your area. Private options are available if NHS waiting times are long.
Are weight loss injections covered by the NHS?
Yes, Mounjaro, Wegovy, and Saxenda are all available through NHS specialist weight management services for eligible adults. However, availability and access criteria vary by region and local ICB. Your GP can advise what's available in your area.
Can I use the BMI calculator to check my eligibility?
Yes. Use our free BMI calculator on this page to find your current BMI instantly. If your BMI is 27 or above, or you have weight-related health conditions, discuss with your GP whether NHS weight loss treatment might be suitable for you. The calculator helps you understand your starting point before that conversation.
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.