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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Metabolic Weight Loss Medication in the UK
Metabolic weight loss through prescription medication is now available to eligible UK adults. If you're looking at weight management options, prescription medications like Mounjaro (tirzepatide) and Wegovy (semaglutide) can support weight loss alongside diet and exercise changes. These GLP-1 and GIP/GLP-1 receptor agonist medications work by helping regulate appetite and how your body processes food. Access in the UK is either through NHS specialist weight management services or private prescription following a clinical assessment. This guide explains your options and how to find out if you're eligible.
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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 and Eligibility
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — 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 alongside lifestyle changes.
- Wegovy (semaglutide) — GLP-1 agonist, once-weekly injection, doses from 0.25 mg to 2.4 mg. Evidence suggests approximately 15% average body weight loss in clinical trials.
- Saxenda (liraglutide) — GLP-1 agonist, once-daily injection, doses up to 3 mg. First GLP-1 approved for weight loss in the UK.
To be eligible for these medications, you typically need a BMI of 30 kg/m² or above, or BMI 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply. Use our free BMI calculator above to check your personal BMI instantly.
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.
Accessing Weight Loss Medication: NHS and Private Routes
NHS access: NICE has approved tirzepatide (Mounjaro) for use in NHS specialist weight management services (tier 3 and 4). Your GP can refer you to your local service, though waiting times and availability vary significantly by region. Many areas have substantial waiting lists.
Private access: GLP-1 medications are available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route does not require an NHS referral and offers faster access, typically within days. Your prescriber will assess your medical history, current medications, and suitability before issuing a prescription.
Track your weight loss progress with our free progress tracker once you begin treatment. Whether you choose NHS or private, combining medication with reduced-calorie diet and increased physical activity gives the best results for sustainable metabolic weight loss.
- 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 metabolic weight loss medication and how does it work?
Metabolic weight loss medications are prescription injectables that work on appetite and hunger hormones. GLP-1 agonists (like Wegovy and Saxenda) and dual GIP/GLP-1 agonists (like Mounjaro) mimic natural gut hormones. They help you feel fuller after smaller meals, reduce food cravings, and support weight loss alongside diet and exercise. Individual results vary, but clinical trials show an average loss of 15–21% body weight.
Am I eligible for prescription weight loss medication on the NHS in the UK?
You may be eligible if your BMI is 30 kg/m² or above, or 27–29.9 kg/m² with a weight-related health condition like diabetes, high blood pressure, or heart disease. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Eligibility is assessed individually. Ask your GP for a referral to specialist weight management services in your area, though availability varies by region.
What's 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 showed similar average weight loss outcomes (15–21% for Mounjaro, ~15% for Wegovy), though individual results vary. Your prescriber will recommend which is most suitable based on your health profile and medical history.
How quickly can I access prescription weight loss medication privately in the UK?
Private access is typically faster than NHS. Following an online clinical assessment with a UK-licensed prescriber, you can usually receive a prescription within days if you're clinically suitable. The medication is then dispensed by a GPhC-registered pharmacy. Costs vary by dose and provider but typically range from £129–£320 per month. NHS access involves referral and may involve waiting lists.
Will weight loss medication work without lifestyle changes?
No. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. They support behaviour change by reducing appetite and cravings, but they're not a replacement for lifestyle changes. The NHS recommends sustainable weight loss of 0.5–1 kg per week. Most people see the best results when combining medication with healthy eating habits and regular exercise.
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.