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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Best Weight Loss App for Weight Management in the UK
When you're looking for the best weight loss app in the UK, you'll find options range from free health tracking tools to prescription weight management medication. If you have a BMI of 30 or above, or 25–29.9 with weight-related health conditions, you may be eligible for prescription weight loss support through the NHS or privately. This guide covers UK-licensed options, how they work, and how to find out if you're eligible. Use our free BMI calculator and GLP-1 weight loss calculator to explore your personal situation.
10,000+ calculations today · NHS-aligned thresholds · 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/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 Management Options
The most clinically effective weight loss apps and tools available in the UK for eligible adults include prescription weight management medication. Three medications are currently licensed in the UK:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 hormone pathways. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, though individual results vary.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Average weight loss in clinical trials was approximately 15% of body weight, alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a daily GLP-1 injection. Less commonly prescribed than the once-weekly options but evidence-based for weight loss support.
These are all prescription-only medicines and require a clinical assessment before being prescribed. Eligibility depends on your BMI, age, and any weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Your GP or a licensed prescriber will assess whether prescription weight management is suitable 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.
NHS vs Private Access — How to Get Started
NHS access: Prescription weight loss medication is available through specialist tier 3 weight management services. You'll need a GP referral and assessment. NHS availability and waiting times vary significantly by region — some areas have long waiting lists.
Private access: Available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route typically offers faster access without NHS waiting lists, though costs vary by dose and provider.
Getting started: Talk to your GP about prescription weight management options, or use our free BMI calculator above to understand your personal BMI category. Your GP can refer you to specialist services, or you can explore private prescribing independently. Either route requires a proper clinical assessment — this ensures the medication is safe and suitable for your individual health.
- 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 best weight loss app if I'm not eligible for prescription medication?
If you don't meet the criteria for prescription weight loss medication, try NHS digital tools like the NHS Weight Loss Plan, MyFitnessPal for calorie tracking, Strava for activity logging, or apps focused on behaviour change. Our free weight converter, BMI calculator, and progress tracker on MyWeightCheck are also useful for tracking your health metrics and weight loss journey without cost.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy, achieved over 68–72 weeks alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly — some people lose more, some less. Your GP or prescriber can discuss realistic expectations based on your personal health.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with a weight-related health condition like type 2 diabetes, high blood pressure, or sleep apnoea. For some ethnic backgrounds (South Asian, Chinese, Black African, Black Caribbean), thresholds are lower. Use our free BMI calculator to check your BMI, then speak to your GP about NHS specialist services in your area.
How do I know which weight loss app or medication is right for me?
The best option depends on your BMI, health conditions, preferences, and eligibility. A licensed prescriber or your GP will assess you individually. Private prescribers and NHS specialists both take into account your medical history, current medications, and personal goals. There's no one-size-fits-all answer — personalised assessment is essential.
Can I use a weight loss app alongside prescription medication?
Yes — prescription weight loss medication works best alongside lifestyle changes. Using a progress tracker app, food diary, or fitness app alongside medication can help you stay motivated and track results. Our free progress tracker and BMI calculator are useful companions to any weight management approach, whether medication or lifestyle-based.
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.