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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Safe Quick Weight Loss: UK Prescription Medication Options
Losing weight safely and effectively is possible with the right approach. In the UK, prescription weight management medications offer evidence-based support for eligible adults alongside lifestyle changes. This guide explains the safe weight loss options available through the NHS and private prescribers, how they work, and whether you might be eligible. While fad diets promise rapid results, medically-supported weight management focuses on sustainable progress—typically 0.5 to 1 kg per week—which is safer and more likely to last.
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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: What's Available
Three prescription medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide), a GLP-1 receptor agonist; and Saxenda (liraglutide), also a GLP-1 agonist. All are injectable and work by helping reduce appetite and food cravings. Clinical trial evidence shows that alongside a reduced-calorie diet and increased physical activity, these medications may help participants lose an average of 15–21% of their body weight, though individual results vary significantly.
- Mounjaro: Once-weekly injection, dual mechanism, doses from 2.5mg to 15mg
- Wegovy: Once-weekly injection, up to 2.4mg maximum dose
- Saxenda: Daily injection, up to 3mg per day
Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Your GP can assess whether prescription weight loss medication is appropriate for your situation.
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: How to Access Weight Management Support
NHS access: Prescription weight loss medication is available through specialist tier 3 weight management services, usually following a GP referral. Availability varies significantly by region and waiting lists can be lengthy. Private access: You can obtain a prescription through a GPhC-registered online prescriber following a clinical assessment, without needing an NHS referral. Costs typically range from £129–£320 per month depending on dose and provider.
To find out if you're eligible, start by calculating your BMI using our free BMI calculator above, then discuss weight management options with your GP. They can advise on NHS availability in your area or discuss whether private prescribing might suit you. Whichever route you choose, success depends on combining medication with a reduced-calorie diet and regular physical activity.
- 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.
How quickly can I lose weight with GLP-1 medication?
Most people see initial weight loss within the first few weeks, with average losses of 0.5–1 kg per week when combined with a reduced-calorie diet. Clinical trials show total weight loss of 15–21% over several months, but individual results vary. Sustainable weight loss is safer than rapid loss.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist (doses up to 15mg weekly), while Wegovy is a GLP-1 agonist only (up to 2.4mg weekly). Clinical trials show Mounjaro may produce slightly greater average weight loss, but both are effective. Your prescriber will recommend the most suitable option for you.
Am I eligible for prescription weight loss treatment on the NHS?
You may be eligible if your BMI is 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. Eligibility varies by region. Contact your GP to discuss NHS specialist services in your area.
Are weight loss injections safe?
All three UK-licensed medications have been through rigorous clinical trials and are approved by the MHRA. Side effects are common but usually manageable and improve over time. Serious side effects are rare. Your GP or prescriber will discuss risks and benefits based on your health.
Can I use our weight loss calculator to estimate my results?
Yes—our GLP-1 weight loss calculator can help you project potential weight loss at different doses based on clinical trial data. Remember this shows average outcomes; your actual results will depend on diet, activity level, and individual factors. Use it alongside our BMI calculator to track your baseline and goals.
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.