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
Free Weight Loss App and UK Prescription Options
A free weight loss app can help you track progress, but many UK adults also benefit from prescription weight management options. If you have a BMI of 30 or above, or 27 with weight-related health conditions, you may be eligible for licensed medications like Mounjaro or Wegovy. These are available through NHS specialist services or private prescribing following clinical assessment. MyWeightCheck combines free tools with evidence-based information to support your weight management journey alongside professional guidance.
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 Weight Loss Medications
Three prescription options are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist administered once weekly. Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks alongside lifestyle changes.
- Wegovy (semaglutide) — a GLP-1 receptor agonist injected once weekly, with average weight loss around 15% in clinical trials.
- Saxenda (liraglutide) — a daily GLP-1 injection, typically prescribed when other options aren't suitable.
All three are prescription-only medicines requiring a clinical assessment. They work by helping reduce appetite and support feeling fuller after meals. Weight loss with these medications is most effective when combined with a reduced-calorie diet and increased physical activity. Individual results vary significantly based on dose, adherence, and personal factors. Our free GLP-1 weight loss calculator can help you explore potential outcomes at different 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.
Eligibility and How to Access
NHS eligibility: Adults with a BMI of 30 or above, or 27–29.9 with weight-related conditions (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease), may qualify. Access is through specialist tier 3 weight management services via GP referral. Waiting lists vary by region, and availability is not uniform across all NHS areas.
Private access: Available through GPhC-registered online prescribing services following a clinical questionnaire. No NHS referral required, though a prescription from a UK-licensed prescriber is essential. You can speak to your GP about whether prescription weight loss medication is appropriate for you, or explore private options independently. Combining our free BMI calculator and progress tracker with professional support maximises your chances of sustainable weight loss.
- 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 difference between a free weight loss app and prescription medication?
A free weight loss app tracks calories, exercise, and progress — helpful for accountability. Prescription medications like Mounjaro and Wegovy actively reduce appetite and help regulate blood sugar, addressing the biological side of weight management. Most effective results combine both: use an app or our free progress tracker alongside medication and lifestyle changes if you're eligible.
Am I eligible for weight loss medication on the NHS?
You may be eligible if your BMI is 30 or above, or 27–29.9 with a weight-related health condition like type 2 diabetes, high blood pressure, or sleep apnoea. Eligibility varies by region. Speak to your GP, who can refer you to specialist weight management services. Private prescribers assess eligibility independently.
How much does prescription weight loss medication cost privately in the UK?
Private Mounjaro and Wegovy typically cost £129–£320 per month depending on dose and provider. Starting doses are cheaper than maintenance doses. NHS prescriptions are free once issued through specialist services, though waiting times can be substantial. Compare costs and waiting times when deciding between NHS and private routes.
Can I use a free weight loss app without medication?
Yes — many people achieve sustainable weight loss through diet, exercise, and tracking alone. A calorie deficit of 500 kcal per day typically results in 0.5 kg per week loss. However, if you have a high BMI or weight-related health conditions, combining an app with professional support or medication may be more effective.
How do I know if GLP-1 medication is right for me?
Only a licensed prescriber can assess suitability after reviewing your medical history, current medications, and health conditions. Start by speaking to your GP, who can discuss options and refer you to NHS services if appropriate. Alternatively, private prescribers conduct online assessments. Our free BMI calculator and GLP-1 weight loss calculator can help you understand your starting point and potential outcomes.
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.