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 Programs in the UK
Finding the right weight loss program depends on your personal circumstances, health profile, and lifestyle. The UK offers several approaches ranging from self-help support through to prescription medication and specialist services. Whether you're looking for NHS weight management support, dietary changes, increased physical activity, or prescription options like GLP-1 weight loss injections, understanding what's available helps you make an informed decision. Our free BMI calculator can help you assess where you currently sit, and our weight loss calculator can show projected outcomes with different approaches.
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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.
The NHS Weight Management Pathway
The NHS provides a structured four-tier approach to weight management. Tier 1 includes self-help resources, digital tools, and community weight management programmes — perfect for anyone wanting to start their weight loss journey. Tier 2 involves primary care-based interventions where your GP offers behaviour change support and monitoring. Tier 3 specialist multidisciplinary weight management services assess your health in detail and may prescribe weight loss medication alongside lifestyle support. Tier 4 covers bariatric (weight loss) surgery for severe obesity with significant health complications.
Access varies significantly by region, and waiting times for specialist services (Tier 3) can be lengthy in many areas. Your GP can refer you to the appropriate tier based on your BMI, health conditions, and previous weight loss attempts. Using our BMI calculator above helps you understand which tier may be relevant for your situation.
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.
Prescription Weight Loss Medication Options
For those with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, prescription weight loss medication may be appropriate. GLP-1 weight loss injections like Wegovy (semaglutide) and Mounjaro (tirzepatide) are licensed in the UK and work by helping regulate appetite and supporting fullness after meals. Clinical trials showed average weight loss of around 15% body weight with these medications, though individual results vary significantly.
Prescription weight loss medications require a clinical assessment to confirm suitability, and are always used alongside reduced-calorie diet and increased physical activity — not instead of them. NHS specialist services and private prescribers both offer access. Try our GLP-1 weight loss calculator to estimate projected outcomes at different doses, and consult your GP or prescriber about eligibility.
- 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's the fastest weight loss program available in the UK?
The NHS recommends losing 0.5–1 kg per week for sustainable results. Faster loss is possible with medical supervision but increases muscle loss risk. GLP-1 weight loss medications combined with diet and exercise typically support faster results than diet alone, though outcomes vary individually. Any gradual weight management programme should be discussed with your GP.
Can I get weight loss medication through the NHS?
Yes. Tirzepatide (Mounjaro) and semaglutide (Wegovy) are approved by NICE for use through NHS specialist weight management services (Tier 3). Access requires referral from your GP and varies by region. Waiting lists can be very long in many areas. Private access is also available through GPhC-registered online prescribing services.
How do prescription weight loss injections compare to diet alone?
Clinical trials show GLP-1 medications help achieve greater weight loss than diet and exercise alone. In STEP trials, Wegovy at the maximum dose supported average weight loss of around 15% body weight. However, these medications work best combined with dietary changes and physical activity — they're tools to support lifestyle changes, not replacements for them.
What's the difference between Mounjaro and Wegovy?
Both are prescription-only injectable medications. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with a maximum dose of 15mg weekly. Wegovy (semaglutide) is a GLP-1 agonist with a maximum dose of 2.4mg weekly. Clinical trials suggest similar average weight loss, but individual responses differ. Your prescriber will advise which is more suitable based on your health.
Are weight loss programs covered by my health insurance?
This depends on your specific insurance policy. Some private health insurance plans cover weight loss medications when prescribed privately, while others don't. NHS treatment is free. Contact your insurance provider directly to understand your cover. Your GP can also advise on NHS options available to you locally.
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.