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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Help With Weight Loss: Prescription Medication in the UK
If you're looking for help with weight loss in the UK, prescription medication may be an option worth discussing with your GP. Several weight loss injections are now licensed in the UK, including Mounjaro and Wegovy, alongside NHS specialist services. Eligibility depends on your BMI, health conditions, and individual circumstances. This guide covers what's available, who qualifies, and how to access support through both NHS and private routes.
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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 Medications Available Now
Three prescription weight loss medications are currently licensed in the UK:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, injected once weekly. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks alongside a reduced-calorie diet and increased activity.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, also injected once weekly. Clinical evidence shows average weight loss of around 14.9% of body weight at the maximum dose.
- Saxenda (liraglutide) — a GLP-1 receptor agonist given as a daily injection, with evidence supporting modest weight loss over time.
All are prescription-only medicines requiring a clinical assessment. Individual results vary significantly, and these medications work best alongside lifestyle changes including diet and physical activity. Use our free GLP-1 weight loss calculator above to see potential weight loss projections at different medication 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.
Who Qualifies for Weight Loss Medication in the UK?
Eligibility for prescription weight loss treatment depends on your BMI and health circumstances. You may qualify if you have 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 cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidelines recommend considering treatment at a lower BMI due to higher health risks at these thresholds. Your GP or a licensed prescriber will assess your individual situation. Check your personal BMI using our free BMI calculator above, then discuss options with your healthcare provider to explore what suits your circumstances.
NHS vs private access works differently: Through the NHS, you'll be referred to a specialist weight management service (tier 3), where a multidisciplinary team assesses suitability and prescribes medication. NHS access is free but availability and waiting times vary significantly by region. Privately, you can have an online consultation with a UK-licensed prescriber without an NHS referral — treatment is faster but involves a cost. Both routes require a proper clinical assessment; neither provides medication without professional evaluation. Speak to your GP first about NHS options in your area, or research GPhC-registered online services if you prefer the private route.
- 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 weight loss medication and weight management?
Weight loss medication such as GLP-1 injections are prescription medicines that help reduce appetite and support weight reduction. Weight management is the broader approach involving diet, exercise, behaviour change, and sometimes medication. The medications are tools to support weight management, not replacements for lifestyle changes.
How much weight will I lose on Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% of body weight on Mounjaro and around 15% on Wegovy, but individual results vary significantly. Some people lose more, some less. Results depend on adherence, lifestyle changes, starting weight, and personal metabolism. Your prescriber can discuss realistic expectations.
Can I get weight loss injections through the NHS?
Yes, some NHS regions offer tirzepatide (Mounjaro) through specialist weight management services (tier 3). However, access is limited and varies by region; waiting lists can be lengthy. Your GP can refer you to check local availability, or you can explore private prescribing options.
What are the main side effects of weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and stomach discomfort, especially when starting or increasing doses. Most side effects reduce over time. Serious side effects are rare but include severe abdominal pain (possible pancreatitis) and allergic reactions — seek immediate medical attention if these occur.
How do I find out if I'm eligible for weight loss medication?
Start by calculating your BMI using our free BMI calculator above. If your BMI is 30 or above, or 27–29 with weight-related health conditions, you may be eligible. Book an appointment with your GP to discuss options, or consult a UK-licensed online prescriber who can assess your suitability following a clinical evaluation.
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.