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
Best Weight Loss Training Program in the UK
Finding the best weight loss training program for you depends on your individual health, circumstances, and goals. In the UK, weight management goes beyond exercise and diet alone — prescription weight loss medications are now available for eligible adults through both NHS and private routes. This guide covers your options, including GLP-1 medications, NHS pathways, and how to determine if prescription support might be right for you. Our free BMI calculator can help you understand your starting point, and our GLP-1 weight loss calculator can show you potential outcomes with medication support.
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 Prescription Weight Loss Options
Three prescription-only medications are currently licensed in the UK for weight management alongside lifestyle changes:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, injected once weekly. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks when combined with a reduced-calorie diet and exercise.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, injected once weekly. Clinical trials showed an average weight loss of approximately 15% of body weight at the maximum dose.
- Saxenda (liraglutide) — A GLP-1 receptor agonist given as a daily injection. Results are comparable to other GLP-1 options.
You are eligible for prescription weight loss medication if you have a BMI of 30 or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, hypertension, or cardiovascular disease. Lower thresholds may apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage. Individual results vary significantly, and these medications are always used alongside dietary changes and increased physical activity, not as a replacement.
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 and How to Get Started
NHS route: Weight loss medications are available through NHS tier 3 specialist weight management services. Ask your GP for a referral. NHS access ensures clinical oversight and is free at point of use, though availability and waiting times vary significantly by region.
Private route: You can access prescription weight loss medication through GPhC-registered online clinics without an NHS referral. A UK-licensed prescriber will conduct an online clinical assessment to confirm eligibility before issuing a prescription. Private prescriptions typically cost £129–£320 per month depending on the medication and dose.
Start by speaking with your GP about weight management options suitable for you. They can discuss whether prescription medication is appropriate, refer you to NHS specialist services, or advise on private access. Our BMI calculator can help you prepare for this conversation by showing your current BMI category and healthy weight range for your height.
- 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 the best weight loss medication available in the UK?
There is no single "best" medication — the most suitable option depends on your individual health, BMI, medical history, and preferences. Mounjaro, Wegovy, and Saxenda are all licensed in the UK. Your GP or a prescriber will assess which is most appropriate for you following a clinical evaluation. Results vary between individuals.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if your BMI is 30 or above, or 27–29.9 with a weight-related health condition such as diabetes or high blood pressure. Ask your GP for a referral to specialist weight management services in your area. Eligibility criteria and availability vary by NHS region.
How much weight can I expect to lose with prescription weight loss medication?
Clinical trials show average weight loss of 15–21% of body weight, depending on the medication and dose. However, individual results vary significantly. Weight loss is most effective when combined with a reduced-calorie diet and increased physical activity. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses.
How quickly do weight loss injections work?
Most people notice reduced appetite and early weight loss within 2–4 weeks. However, meaningful weight loss typically becomes apparent over 8–12 weeks as doses are gradually increased. The full benefit is usually seen after 16–20 weeks of treatment at therapeutic doses.
Can I get prescription weight loss medication privately without seeing my GP first?
Yes. Private online clinics can assess and prescribe eligible patients without an NHS referral. However, it is still recommended to inform your GP about any weight loss treatment you are receiving, as they need to know about all medications and health changes for your safety.
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.