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 App UK — What Actually Works
Finding the right weight loss app in the UK means choosing a tool that aligns with NHS guidance and your personal health goals. The best apps combine three key features: accurate tracking, evidence-based information, and integration with prescription weight loss medication if needed. Rather than relying on apps alone, many UK adults find success by combining digital tools with professional support, lifestyle changes, and—where appropriate—prescription weight management. This guide covers what to look for and how to get started with your weight loss journey.
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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.
What Makes a Weight Loss App Effective in the UK?
The best weight loss apps in the UK offer more than just calorie counting. They should align with NHS weight management guidelines, which recommend a safe weight loss rate of 0.5–1 kg per week. Look for apps that:
- Track consistently: Daily logging of weight, meals, and activity helps identify patterns
- Calculate BMI: A built-in BMI calculator lets you monitor progress against NHS healthy weight thresholds (18.5–24.9 for most adults)
- Provide evidence-based content: Information backed by NHS or NICE guidance, not fad diet claims
- Support prescription integration: If you're considering weight loss medication such as GLP-1 injections, the app should track medication alongside lifestyle changes
- Use UK measurements: Apps designed for the UK market work in stone, pounds, and kilograms—not just imperial units
The most effective approach combines an app with professional support. Use our free BMI calculator above to establish your starting point, then choose an app that supports consistent progress tracking.
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 Prescription Weight Loss Fits Into App-Based Tracking
If you're exploring prescription weight loss medication through NHS specialist services or private prescribing, your tracking app becomes even more valuable. Apps like MyFitnessPal, Lose It!, and NHS-approved tools such as the Better Health app can log meals and weight changes, which your prescriber will review during appointments.
For those considering GLP-1 weight loss injections (such as Mounjaro or Wegovy), evidence from clinical trials shows weight loss averages around 15–21% of body weight over 68–72 weeks when combined with lifestyle changes. Try our free GLP-1 weight loss calculator above to estimate potential outcomes at different doses. Track your progress using our free progress tracker alongside your chosen app to monitor both weight and medication tolerance.
- 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 free weight loss app available in the UK?
The NHS-approved Better Health app is free and designed specifically for UK adults. MyFitnessPal and Lose It! are also popular free options. For the most comprehensive approach, combine any app with free tools like our BMI calculator and weight converter to track progress against NHS healthy weight thresholds. The best app is the one you'll use consistently.
Should I use an app instead of seeing my GP for weight loss?
No. Apps are helpful tools but not a substitute for professional advice. If you have significant excess weight or weight-related health conditions, start with your GP. They can refer you to NHS specialist weight management services (tier 3) where you may receive prescription support alongside digital tracking. Apps work best alongside professional guidance, not instead of it.
Can a weight loss app help if I'm taking Mounjaro or Wegovy?
Yes. Tracking your meals, weight, and side effects in an app provides valuable data for your prescriber. Many UK adults use MyFitnessPal or Lose It! alongside GLP-1 medication. Use our weight loss calculator to estimate projected outcomes, and log progress consistently in your chosen app. Consistent data helps your prescriber adjust your dose or support if needed.
How do I choose between weight loss apps?
Look for apps that work in UK measurements (stone and pounds), offer evidence-based content aligned with NHS guidance, and have strong user reviews. Try one for 2–4 weeks to see if you'll use it consistently. Many UK adults find success combining apps with our free BMI calculator, weight converter, and progress tracker for a complete tracking system.
What's the difference between a weight loss app and a diet app?
Weight loss apps focus on long-term weight management, exercise tracking, and behaviour change, while diet apps often promote specific eating plans. The best weight loss apps support sustainable healthy weight management alongside NHS recommendations for 0.5–1 kg weekly loss. Look for apps that emphasize behaviour change and lifestyle, not quick fixes.
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.