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
Prescription Diet Pills and Weight Loss Options in the UK
Prescription diet pills are just one option for weight loss in the UK. If you're considering how to lose weight safely, you have several routes available through the NHS and private services. These range from free lifestyle support programmes to prescription medications like GLP-1 injections (Mounjaro and Wegovy) and bariatric surgery. Understanding what's available helps you and your GP find the right approach for your situation.
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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.
Weight Loss Options Available in the UK
The UK offers a structured pathway for weight management, from self-help to specialist intervention. Here's what's available:
- Tier 1 (Self-help): Free NHS resources, online tools, community weight management programmes, and diet apps. Use our free BMI calculator and weight loss calculator to understand your starting point and potential progress.
- Tier 2 (Primary Care): Support from your GP, behaviour change services, and evidence-based weight loss programmes like the NHS Weight Loss Plan.
- Tier 3 (Specialist Services): Multidisciplinary weight management clinics where prescription medications are prescribed. Includes GLP-1 medications such as Wegovy (semaglutide) and Mounjaro (tirzepatide).
- Tier 4 (Surgery): Bariatric surgery for severe obesity with significant health complications, typically BMI over 35.
Prescription weight loss medications in the UK are prescription-only and require clinical assessment. Access varies significantly by region and local NHS capacity.
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.
How to Choose the Right Weight Loss Approach
The best weight loss method depends on your personal situation, health status, and goals. Consider these factors:
- Your BMI: Use our weight converter and BMI calculator to establish your current BMI. Those with a BMI of 30+ or 27+ with weight-related conditions may be eligible for prescription options.
- Medical conditions: Type 2 diabetes, high blood pressure, or sleep apnoea may make you eligible for GLP-1 medications or specialist referral.
- Previous attempts: If lifestyle changes alone haven't worked, prescription medication or specialist support may help.
- Your GP is the starting point. Discuss your goals and ask about NHS tier 3 referral or options available in your area.
Sustainable weight loss combines whichever approach suits you with long-term lifestyle changes. Track your progress with our free progress tracker to stay motivated.
- 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 difference between prescription diet pills and over-the-counter weight loss products?
Prescription weight loss medications are clinically licensed, evidence-based medicines requiring a prescription and medical assessment. Over-the-counter products are unregulated, often lack strong evidence, and may be ineffective or unsafe. In the UK, prescription options like GLP-1 medications have undergone rigorous clinical trials and are monitored by the MHRA.
Are prescription weight loss injections like Mounjaro and Wegovy available on the NHS?
Yes, both Mounjaro (tirzepatide) and Wegovy (semaglutide) are approved by NICE for use within NHS specialist weight management services (tier 3). However, NHS access is limited and varies by region. Waiting lists can be very long. They are also available privately through UK-licensed prescribers following an online clinical assessment.
How much weight can I expect to lose with prescription medications?
Clinical trials show that GLP-1 medications can help achieve average weight losses of 14–21% of body weight over several months when combined with dietary changes and physical activity. However, individual results vary significantly. Your GP or prescriber can discuss realistic expectations based on your personal circumstances.
Is sustainable weight loss possible without prescription medication?
Yes. Many people achieve lasting weight loss through dietary changes, increased physical activity, and behaviour change support. A calorie deficit of around 500 kcal per day typically results in losing 0.5 kg per week. The NHS offers free tier 1 and tier 2 support through GPs and community programmes — these are often effective first steps.
How do I access prescription weight loss treatment through the NHS?
Start by speaking with your GP about weight management options. If you meet eligibility criteria (BMI 30+, or 27+ with health conditions), your GP can refer you to your local tier 3 specialist weight management service. However, availability, assessment criteria, and waiting times vary significantly across England, Scotland, Wales, and Northern Ireland.
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.