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
Alli Weight Loss Capsules and UK Weight Management Options
Alli (orlistat) is an over-the-counter weight loss capsule available in UK pharmacies. However, if you're looking for evidence-based weight management options in the UK, prescription medications like Mounjaro, Wegovy, and Saxenda offer stronger clinical evidence for weight loss. This guide explains what's available on the NHS, through private prescribing, and who may be eligible for prescription weight loss medication in the UK.
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.
Prescription Weight Loss Options Available in the UK
For adults seeking structured weight management in the UK, prescription medications offer clinical evidence-backed alternatives. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist approved for weight management. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks. Wegovy (semaglutide) is a GLP-1 injection available once weekly, with average weight loss of around 15% in clinical trials. Saxenda (liraglutide) is a daily GLP-1 injection option. All three are prescription-only medicines that require a clinical assessment before being prescribed.
- Mounjaro: doses from 2.5 mg to 15 mg weekly
- Wegovy: doses from 0.25 mg to 2.4 mg weekly
- Saxenda: doses from 0.6 mg to 3 mg daily
These medications work alongside a reduced-calorie diet and increased physical activity for best results. Use our free GLP-1 weight loss calculator to explore potential weight loss projections 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.
NHS vs Private Access to Weight Loss Medication
NHS access: Prescription weight loss medications are available through tier 3 specialist weight management services following a GP referral. Availability varies significantly by region, and waiting lists can be lengthy. Your GP can assess your eligibility and refer you if appropriate.
Private access: Available through GPhC-registered online prescribing services following an online clinical assessment. This route does not require an NHS referral and offers faster access, though costs typically range from £129–£320 per month depending on dose.
To understand your personal weight management needs, check your BMI using our free BMI calculator, which helps determine if you may be eligible for prescription support.
- 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 is Alli and is it available in the UK?
Alli (orlistat 60 mg) is an over-the-counter weight loss capsule available in UK pharmacies without prescription. It works by reducing fat absorption in the digestive system. However, it has limited clinical evidence compared to prescription GLP-1 medications like Mounjaro and Wegovy.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, heart disease), may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds. A prescriber will assess your individual eligibility.
How do I access prescription weight loss medication on the NHS?
Speak to your GP about referral to a tier 3 specialist weight management service. They will assess your health and eligibility. NHS availability varies by region; some areas have long waiting lists. Your GP can discuss whether prescription medication is appropriate for you.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with higher average weight loss (15–21%) in trials. Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Both are once-weekly injections. Individual results vary significantly, and a prescriber will recommend the most suitable option.
Can I use prescription weight loss medication without dietary changes?
No. Prescription weight loss medications like Mounjaro, Wegovy, and Saxenda are designed to be used alongside a reduced-calorie diet and increased physical activity. They support weight loss by reducing appetite and food cravings, but lifestyle changes are essential for sustainable results.
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.