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 Free Weight Loss Apps in the UK
Free weight loss apps can help track calories, exercise, and progress—but they work best alongside other strategies. For UK adults looking to lose weight, free apps are just one option. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, prescription weight management medication may also be available through the NHS or private prescribers. This guide explains both free digital tools and licensed medication options to help you find the right weight management approach for your 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 Loss Options
If free apps alone aren't delivering results, prescription weight loss medication is available in the UK for eligible adults. Three medications are currently licensed for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that works via dual GIP and GLP-1 pathways. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks, alongside diet and exercise.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. STEP trials demonstrated approximately 15% average weight loss at the maximum 2.4 mg dose.
- Saxenda (liraglutide) — a daily GLP-1 injection, the longest-established option in the UK.
All three are prescription-only and require clinical assessment before being prescribed. Individual results vary significantly based on adherence, diet, and lifestyle changes.
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 and Next Steps
NHS access: Referral to a specialist tier 3 weight management service through your GP. Availability and waiting times vary significantly by region (ICB). Many areas have lengthy waiting lists.
Private access: Through GPhC-registered online prescribers following an online clinical consultation. Available without NHS referral. Costs range from approximately £129–£320 per month depending on dose.
Start by speaking with your GP about your weight loss goals. They can assess your eligibility, discuss whether you qualify for NHS specialist services, and explain all available options. Use our free GLP-1 weight loss calculator to understand potential outcomes, and the BMI calculator to determine your starting point for the conversation.
- 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.
Are free weight loss apps effective on their own?
Free apps can help with tracking and accountability, which supports some weight loss. However, studies show they work best combined with behaviour change support, dietary changes, and exercise. For sustainable weight loss, most people need more than an app alone—professional support or medication may help.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above qualify. Those with a BMI of 27–29.9 may qualify if they have weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Your GP or a licensed prescriber will assess your individual eligibility following a clinical consultation.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections, but Mounjaro (tirzepatide) uses dual GIP and GLP-1 pathways and showed slightly higher average weight loss (15–21%) in trials versus Wegovy's 15%. Mounjaro starts at 2.5 mg and goes up to 15 mg; Wegovy starts at 0.25 mg and tops out at 2.4 mg. Individual response varies.
Can I get Mounjaro or Wegovy on the NHS?
Yes, tirzepatide (Mounjaro) is NICE-approved and available through NHS specialist tier 3 weight management services. However, availability, eligibility criteria, and waiting times vary significantly by region. Ask your GP about referral options in your area, as some ICBs have extended waiting lists.
How quickly will I lose weight on prescription medication?
Weight loss typically begins within the first few weeks but is gradual. Most people see meaningful loss after 8–12 weeks at therapeutic dose. Clinical trials show average losses of 15–21% over 72 weeks with Mounjaro, but individual results vary. Medication works best alongside reduced-calorie diet and increased physical activity.
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.