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
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Weight Loss App and Prescription Medication Options in the UK
A weight loss app can help track progress and support lifestyle changes, but many people in the UK also have access to prescription weight management medication. If you're looking to lose weight, understanding both digital tools and prescription options available through the NHS or private prescribers is essential. This guide covers UK-licensed medications, eligibility criteria, and how to start a conversation with your GP about weight loss support. Use our free BMI calculator and GLP-1 weight loss calculator to assess your starting point and explore what options may be suitable 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.
UK-Licensed Prescription Weight Loss Medications
Three prescription-only medications are currently licensed in the UK for weight management. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks. Wegovy (semaglutide) is also a once-weekly GLP-1 injection, with average weight loss of around 15% of body weight in trials. Saxenda (liraglutide) is a daily GLP-1 injection, requiring five injections per week.
- All three are prescription-only and require clinical assessment before prescribing
- Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea
- Individual results vary significantly — weight loss medication works alongside reduced-calorie diet and increased physical activity
- Try our GLP-1 weight loss calculator to see projected outcomes at different medication doses
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 Access vs Private Prescribing in the UK
Access to prescription weight loss medication in the UK differs depending on whether you go through the NHS or private routes. Through the NHS, your GP can refer you to specialist weight management services (tier 3), where a multidisciplinary team assesses eligibility. NHS access varies significantly by region and waiting lists can be lengthy. Through private prescribing, you can access medication via GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber — without waiting for NHS referral.
Either way, your eligibility assessment will consider your BMI, weight-related health conditions, and medical history. Start by speaking to your GP about your weight loss goals — they can advise you on local NHS options or discuss private alternatives. Using a weight loss app to track your progress alongside medication can significantly improve outcomes.
- 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.
Can a weight loss app replace prescription medication?
A weight loss app is a useful support tool for tracking calories, exercise, and progress, but prescription weight loss medications like Mounjaro and Wegovy work through hormone pathways to reduce appetite. Apps and medication are most effective together. Apps help with accountability; medication addresses biological appetite signals. Your GP can advise which approach suits you best.
Who is eligible for prescription weight loss medication on the NHS?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease), may be eligible. Lower BMI thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your eligibility and refer you to specialist services if appropriate.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and around 15% with Wegovy over several months, alongside diet and exercise. Individual results vary significantly — some people lose more, others less. Use our GLP-1 weight loss calculator to see projected outcomes. Weight loss depends on adherence, lifestyle changes, dose, and individual metabolism.
Is prescription weight loss medication available privately in the UK?
Yes. Private UK-licensed prescribers can issue prescriptions for Mounjaro and Wegovy following an online clinical assessment. These are dispensed by GPhC-registered pharmacies. Private access typically costs £129–£320 per month depending on dose and provider. No NHS referral is required, though your GP should be informed of any medication you're taking.
What's the difference between a weight loss app and using our weight loss calculator?
A weight loss app is typically a long-term tracking tool that logs daily calories, exercise, weight, and progress. Our GLP-1 weight loss calculator on this page projects potential weight loss outcomes at different medication doses alongside lifestyle changes. Use the calculator to estimate medication effectiveness, then use a weight loss app to track real progress over time.
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.