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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Week Weight Loss Diet: UK Prescription Medication Options
If you're looking for effective weight management in the UK, prescription medications can play an important role alongside dietary changes and increased physical activity. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results. Several prescription options are now available through the NHS and private prescribing for eligible adults. This guide covers what's available, who qualifies, and how to access weight management support in the UK. Your GP can help you determine the right approach for your individual circumstances.
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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 medications are licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All three are GLP-1 receptor agonists (Mounjaro is a dual GIP/GLP-1 agonist) that work by reducing appetite and helping you feel fuller after eating.
Mounjaro is a once-weekly injection with doses ranging from 2.5 mg to 15 mg. Clinical trials showed average weight loss of approximately 15–21% of body weight over 72 weeks, alongside a reduced-calorie diet and physical activity. Wegovy is also a once-weekly injection (0.25 mg to 2.4 mg) with clinical trial results showing average weight loss of around 15% of body weight. Saxenda is a daily injection with a maximum dose of 3 mg.
All three medications are prescription-only and require a clinical assessment to determine eligibility. Individual results vary significantly. These medications work best when combined with lifestyle changes, not as replacements for them.
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: You can be referred to a specialist weight management service (tier 3) by your GP if you meet eligibility criteria. NHS services assess your BMI, health conditions, and readiness for treatment. However, NHS availability varies significantly by region, and waiting lists can be lengthy in many areas.
Private access: You can access prescription weight loss medication through GPhC-registered online prescribers without NHS referral. This typically involves an online consultation where a licensed prescriber assesses your suitability. Costs vary by provider and dose, ranging from approximately £129–£320 per month.
Next step: Start by speaking with your GP about weight management options. They can discuss NHS referral, assess your eligibility, and advise on the best approach for you. Calculate your BMI using our free BMI calculator above to understand your current weight status and health context.
- 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 weight loss per week is realistic with prescription medication?
The NHS recommends 0.5–1 kg per week for sustainable weight loss. Prescription medications like Mounjaro and Wegovy can support this when combined with a reduced-calorie diet and physical activity. Clinical trials showed average weight loss of 15–21% over several months, but individual results vary. Your prescriber will monitor your progress.
Am I eligible for prescription weight loss medication in the UK?
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, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. Your GP or a licensed prescriber can assess your individual eligibility.
How do I know if prescription medication is right for me?
A clinical assessment with your GP or a licensed prescriber will determine suitability. They'll review your medical history, current medications, BMI, and weight-related health conditions. Prescription weight loss medication works best alongside lifestyle changes, not as a standalone solution. Your prescriber will discuss risks, benefits, and alternatives with you.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections but use different mechanisms. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with clinical trial results showing average weight loss of 15–21%. Wegovy (semaglutide) is a GLP-1-only agonist with average weight loss around 15%. Individual responses vary. Your prescriber can advise which is more suitable for you.
Can I access weight loss medication through the NHS?
Yes, through specialist tier 3 weight management services. Your GP can refer you if you meet criteria. NHS availability and waiting times vary significantly by region. Private prescription through licensed UK prescribers is an alternative if you want faster access. Track your weight progress over time using our free progress tracker to monitor results.
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.