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 and Options in the UK
Weight loss drugs are just one option in a range of approaches available to help UK adults manage their weight safely and sustainably. From free NHS support and lifestyle changes through to prescription medication and bariatric surgery, the right choice depends on your individual circumstances, BMI, and health conditions. This guide covers all available options, how to access them, and how to choose the approach that's right for you.
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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.
Understanding Your Weight Loss Options in the UK
The NHS recognises four tiers of support for weight management. Tier 1 includes free community programmes, online tools, and self-help resources — this is often the first step and is available to everyone through their GP or directly. Tier 2 offers primary care-based interventions, including behaviour change programmes like the NHS Weight Loss Plan, which provides free structured support over 12 weeks.
Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss medications may be considered. This requires a GP referral and is delivered through NHS specialist centres — though waiting times vary significantly by region. Tier 4 covers bariatric (weight loss) surgery for severe obesity with significant health complications, also accessed through specialist NHS services.
Use our free BMI calculator above to understand your starting point and which tier may be appropriate for you.
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 in the UK
Prescription weight loss drugs are available through both NHS specialist services and private prescription. UK-licensed options include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide) — all GLP-1 or dual GIP/GLP-1 receptor agonist injections. These medications work alongside a reduced-calorie diet and increased physical activity, not instead of them.
To access prescription weight loss medication, you'll need a clinical assessment by a GP or licensed prescriber. Our GLP-1 weight loss calculator can help you understand how these medications work and estimate potential weight loss at different doses. Eligibility is based on BMI, weight-related health conditions, and individual health factors — your prescriber will assess 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.
What's the difference between NHS and private weight loss support?
NHS weight loss support is free but often involves waiting lists, particularly for specialist tier 3 services. Private options are available immediately through online prescribing services and private clinics, but come at personal cost. Both require assessment; NHS typically involves GP referral, while private involves online clinical consultation with a UK-licensed prescriber.
How do I know which weight loss approach is right for me?
Start by calculating your BMI using our free BMI calculator above and speaking with your GP. Lifestyle changes work for many people and are always the foundation. If lifestyle alone isn't achieving results after 3–6 months, your GP can discuss tier 2 programmes or specialist referral. Prescription medication is considered when BMI is 30+ or 27+ with weight-related health conditions.
Are weight loss drugs safe to use long-term?
UK-licensed weight loss medications like Mounjaro and Wegovy are approved for ongoing use with medical supervision. However, they're prescription-only and require regular monitoring. Individual suitability varies — some people experience side effects that mean stopping is advisable. Always discuss long-term use with your prescriber, who will assess safety for your circumstances.
Can I combine weight loss drugs with lifestyle changes?
Yes — in fact, prescription medications are designed to work alongside dietary changes and increased physical activity, not replace them. The evidence shows that weight loss is best achieved and sustained when medication supports lifestyle changes rather than being used alone. Your healthcare team can guide you on combining approaches safely.
What's sustainable weight loss in the UK?
The NHS recommends losing 0.5 to 1 kg (1–2 lbs) per week for sustainable results. This typically requires a calorie deficit of around 500 kcal per day. Faster weight loss is possible with medical support but carries higher risks of muscle loss and isn't recommended without supervision. Track your progress safely using our free progress tracker.
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.