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
Free tracker included with every download this week
Weight Loss Drugs On NHS
The NHS offers prescription medication options for weight management, including tirzepatide (Mounjaro), semaglutide (Wegovy), and liraglutide (Saxenda). These are licensed weight loss drugs available in the UK for eligible adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Access varies significantly by region, and understanding your eligibility and how to start the conversation with your GP is the first step towards exploring these evidence-based options for weight management.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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
Three prescription-only medications are licensed in the UK specifically for weight management. Mounjaro (tirzepatide) is a once-weekly injection that activates dual GIP and GLP-1 pathways—clinical trials showed participants lost an average of 15–21% of body weight, though results vary. Wegovy (semaglutide) is a once-weekly GLP-1 injection; the STEP-1 trial demonstrated approximately 15% average weight loss. Saxenda (liraglutide) is a daily GLP-1 injection administered once each day.
All three are prescription-only and require a clinical assessment before being prescribed. They are typically used alongside reduced-calorie diet and increased physical activity—medication alone is not the complete solution. Individual response varies significantly, and not everyone will achieve the same results.
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 Routes
NHS access: Weight loss medications are available through specialist tier 3 weight management services. Your GP can refer you, but availability, waiting times, and eligibility thresholds vary considerably by region and integrated care board (ICB). Some areas have long waiting lists; others may have limited access depending on local commissioning decisions.
Private route: Licensed medications are available through private prescribing via online clinics and GPhC-registered pharmacies. This typically involves a digital consultation with a UK-licensed prescriber and costs range from approximately £129–£320 monthly depending on dose. Private access does not require NHS referral but does require a clinical assessment to ensure suitability.
- 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.
Who is eligible for weight loss drugs on the NHS?
Adults with a BMI of 30 kg/m² or above are typically eligible. Those with a BMI of 27–29.9 with at least one weight-related condition (type 2 diabetes, prediabetes, high blood pressure, high cholesterol, sleep apnoea, or previous cardiovascular disease) may also qualify. Lower thresholds may apply for South Asian, Chinese, Black African, or Black Caribbean adults due to increased health risks at lower BMI.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections licensed for weight management. Mounjaro (tirzepatide) uses a dual GIP and GLP-1 mechanism and showed average weight loss of 15–21% in trials. Wegovy (semaglutide) uses GLP-1 alone and showed approximately 15% average weight loss. Mounjaro has a higher maximum dose (15 mg) versus Wegovy (2.4 mg). Individual response varies, and a prescriber will advise which is more appropriate.
How long do I need to take weight loss medication?
Duration depends on your individual health goals and response. Many people continue medication long-term if they are tolerating it well and seeing benefits, as weight often returns when medication is stopped. Your prescriber will review your progress regularly and discuss whether continued treatment remains appropriate for your circumstances.
What happens if I can't access weight loss drugs on the NHS?
If your local NHS service has long waiting lists or limited availability, private prescribing through registered online clinics is an option. Alternatively, your GP may recommend tier 1–2 support including structured behaviour change programmes, digital weight management tools (like MyWeightCheck's free BMI calculator and progress tracker), or community weight management programmes in your area.
Are weight loss drugs assured to work?
No. While clinical trials showed average weight loss, individual results vary significantly. Some people lose more, some less, and a small proportion may not respond as expected. Weight loss medications work best alongside sustainable lifestyle changes—reduced-calorie diet, increased physical activity, and behaviour change. They are a tool to support weight management, not a assured solution.
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.