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
Top Rated Weight Loss Programs in the UK
If you're looking to lose weight in the UK, you have several evidence-based options available. These range from NHS-supported lifestyle programmes and dietary approaches to prescription weight loss medications and specialist services. The most effective programmes combine dietary changes, increased physical activity, and professional support. Your GP can help you find the right weight management option based on your individual health needs and circumstances. Using our free BMI calculator above can help you understand your current weight status and whether you might benefit from structured weight loss support.
10,000+ calculations today Β· NHS-aligned thresholds Β· 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/mΒ²).
While BMI isn't a perfect measure β it doesn't account for muscle mass, bone density, or fat distribution β 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 β 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.
NHS Weight Loss Programmes and Medical Options
The NHS weight management pathway offers four tiers of support, from self-help digital tools to specialist services. Many NHS areas provide free weight loss programmes through tier 2 primary care services, including behaviour change counselling and structured diet support. For prescription weight loss medication, GPs can refer eligible adults to tier 3 specialist weight management services.
Top-rated prescription options include:
- Wegovy (semaglutide) β Once-weekly GLP-1 injection. Clinical trials showed an average weight loss of around 15% body weight. Prescription-only and requires clinical assessment.
- Mounjaro (tirzepatide) β Once-weekly dual GIP/GLP-1 injection. Clinical data suggests an average weight loss of 15β21% body weight. Also prescription-only with clinical assessment required.
- Saxenda (liraglutide) β Daily GLP-1 injection. Another licensed prescription option for weight management.
All prescription weight loss medications work alongside reduced-calorie diet and physical activity β they are not replacements for lifestyle change. Individual results vary significantly.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care β 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 β 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 β completely free.
Lifestyle-Based Weight Loss Programmes and Getting Started
Evidence-based lifestyle programmes remain highly effective. The NHS Weight Loss Plan is a free digital programme combining diet, exercise, and behaviour change support. Many private weight loss programmes, fitness apps, and group schemes also offer structured support with proven track records.
To find the right programme for you: start by calculating your current BMI using the free BMI calculator on this page, discuss your weight management goals with your GP, and ask about available options in your area. Your GP can assess eligibility for prescription medications if lifestyle approaches alone are not sufficient. You can also track your progress with our free progress tracker once you've started your chosen programme.
- 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 β 5mg β 7.5mg β 10mg β 12.5mg β 15mg
- GLP-1 receptor agonist
- Up to 15β17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg β 0.5mg β 1mg β 1.7mg β 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 | 15β22.5% | 12β17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20β32 weeks | 16β20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | Β£150βΒ£250/month | Β£150βΒ£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 β 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 most effective weight loss program in the UK?
The most effective programme varies by individual. Evidence shows that combining dietary changes (typically a calorie deficit of 500 kcal/day), regular physical activity, and professional support or medication produces the best results. NHS weight management services are free and evidence-based. Prescription weight loss medications like Wegovy and Mounjaro have strong clinical trial data but require GP assessment. Individual results depend on commitment, health factors, and programme fit.
Can I get weight loss medication on the NHS?
Yes, if eligible. NHS tier 3 specialist weight management services can prescribe Mounjaro, Wegovy, and Saxenda for eligible adults. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions. Access and waiting times vary significantly by region (ICB). Your GP can refer you to your local specialist service. Some people also access prescription weight loss medication through private online prescribing with a UK-licensed prescriber.
How much weight can I expect to lose?
This varies significantly between individuals and depends on the programme, your commitment, genetics, and current health. NHS guidance recommends losing 0.5β1 kg per week for sustainable results. Prescription weight loss medications show average weight loss of 15β21% body weight in clinical trials, but this is alongside diet and exercise. Many lifestyle programmes result in 5βclinically studied weight loss over 6β12 months, which still provides meaningful health benefits.
How do I know if I need weight loss support?
Calculate your BMI using our free BMI calculator to understand your weight status. The NHS recommends weight management support if your BMI is 25 or above (or lower for certain ethnic groups). Your GP can also assess whether you have weight-related health conditions that would benefit from structured support. Even small amounts of weight loss (5% of body weight) can improve blood pressure, blood sugar control, and overall health.
What's the difference between Wegovy and Mounjaro?
Both are once-weekly prescription injections for weight loss, but they work slightly differently. Wegovy (semaglutide) is a GLP-1 receptor agonist. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, meaning it activates two hormone pathways. Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15β21% vs around 15%), but individual results vary. Both require prescription and clinical assessment.
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.