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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Face Weight Loss: Prescription Medication Options in the UK
When you lose weight, your face often changes noticeably — cheeks become more defined, jawlines sharpen, and the overall appearance can shift significantly. If you're considering weight management through prescription medication in the UK, several licensed options are available through the NHS or private prescribing. This guide covers the prescription weight loss medications available to UK adults, eligibility criteria, and how to access them. Calculate your personal BMI using our free BMI calculator to understand where you currently stand within NHS guidelines, then explore whether prescription medication might support your weight loss journey alongside diet and exercise.
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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-only medications are currently licensed for weight management in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All are GLP-1 receptor agonists (or dual GIP/GLP-1 agonists in Mounjaro's case) that work by regulating appetite and helping you feel fuller after smaller meals.
- Mounjaro: Dual GIP and GLP-1 agonist, once-weekly injection, doses from 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% body weight.
- Wegovy: GLP-1 agonist only, once-weekly injection, doses up to 2.4 mg. Clinical trials demonstrated average weight loss of approximately 15% body weight.
- Saxenda: GLP-1 agonist, once-daily injection, maximum 3 mg dose. Typically produces more modest weight loss than weekly options.
All three medications require a prescription and clinical assessment. Individual results vary significantly, and weight loss medication is most effective when combined with reduced-calorie diet and increased physical activity. Use our GLP-1 weight loss calculator to explore projected 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 Access vs Private Prescription in the UK
In the UK, weight loss medication access differs between NHS and private routes. NHS access is through specialist tier 3 or tier 4 weight management services — your GP can refer you, though waiting lists vary significantly by region and can extend months to years. Private prescription access is available through GPhC-registered online prescribing services following an online clinical assessment, typically without waiting lists.
To find out if you're eligible, start by checking your BMI using our free weight converter and BMI calculator. Adults with a BMI of 30 or above, or 27–29 with weight-related conditions (type 2 diabetes, high blood pressure, sleep apnoea), may qualify. Ethnicity-adjusted thresholds apply for South Asian, Black African, Black Caribbean, and Chinese backgrounds. Speak with your GP about NHS weight loss options in your area, or explore private prescribing if NHS waiting times are a barrier to starting treatment.
- 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.
Can I get weight loss injections on the NHS in the UK?
Yes. Mounjaro, Wegovy, and Saxenda are all NHS-approved for weight management. Access is through specialist weight management services (tier 3/4), which your GP can refer you to. However, availability and waiting times vary significantly by region. Ask your GP about your local options.
What is the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Clinical trials show Mounjaro achieved slightly higher average weight loss (15–21% vs 15%), but individual results vary. Your prescriber will recommend the most suitable option.
How do I know if I'm eligible for prescription weight loss medication?
You may be eligible if your BMI is 30 or above, or 27–29 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, heart disease). If you're of South Asian, Black African, Black Caribbean, or Chinese heritage, lower thresholds may apply. Your GP or a licensed prescriber will assess your individual situation.
How much weight can I realistically expect to lose with these medications?
Clinical trials show average weight loss of 15–21% of body weight over several months to a year, depending on the medication and dose. However, individual results vary significantly based on genetics, diet, exercise, and other factors. Our GLP-1 weight loss calculator can help you estimate potential outcomes based on clinical data.
Are weight loss injections safe? What are the main side effects?
GLP-1 medications are prescription-only and considered safe when used as directed, though they do have side effects. Most common: nausea, diarrhoea, vomiting, and constipation — typically mild and temporary. Serious side effects are rare but can include pancreatitis or gallbladder problems. Your GP or prescriber will discuss risks and monitor your progress throughout treatment.
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.