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
Want Weight Loss? Here's What You Need to Know
If you want weight loss, you have several options available in the UK — from lifestyle changes and NHS support to prescription medications. Weight management is a personal health decision, and understanding what's available can help you choose an approach that works for you. Whether you're looking to improve your health, reduce disease risk, or feel better physically, this guide covers evidence-based weight loss strategies and how to access them through the NHS or privately.
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.
Weight Loss Options in the UK
If you want weight loss, the NHS recommends starting with lifestyle changes: a reduced-calorie diet and increased physical activity can achieve sustainable results. The NHS aims for a loss of 0.5 to 1 kg per week, which is safe and sustainable long-term.
NHS Weight Management Pathway:
- Tier 1: Self-help and digital tools (like the free tools on this page)
- Tier 2: Primary care support and behaviour change programmes
- Tier 3: Specialist weight management services where prescription weight loss medication may be offered
- Tier 4: Bariatric surgery for severe obesity with health complications
Prescription weight loss medications are available on the NHS through specialist services or privately through licensed prescribers. These include GLP-1 receptor agonists like semaglutide (Wegovy) and tirzepatide (Mounjaro). In clinical trials, these medications helped participants lose an average of 15–21% of their body weight alongside lifestyle changes — though individual results vary significantly.
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.
Getting Started With Weight Loss
Start by calculating your current BMI using our free BMI calculator above — this gives you a baseline and helps you track progress. If you have a BMI of 25 or above, losing even 5% of your body weight can improve blood pressure, blood sugar control, and joint health.
For personalised guidance, speak to your GP, who can assess your health, rule out underlying conditions, and discuss whether prescription weight loss medication is appropriate for you. You can also track your weight loss journey using our free progress tracker. Whether you choose lifestyle changes alone or combine them with medication, sustainable weight loss requires consistency — expect results to take time, but the long-term health benefits are significant.
- 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.
How much weight can I expect to lose?
This varies individually. Clinical trials show that prescription GLP-1 medications help some people lose 15–21% of body weight alongside diet and exercise. Lifestyle changes alone typically result in 0.5–1 kg loss per week. Your GP can discuss realistic expectations for your situation.
What is the difference between Wegovy and Ozempic?
Both contain semaglutide, but Wegovy is licensed specifically for weight management in the UK at a dose of 2.4 mg weekly. Ozempic is approved for type 2 diabetes (up to 2 mg) and is not licensed for weight loss — using it off-label for weight loss is not recommended.
Can I get weight loss medication on the NHS?
Yes, through specialist tier 3 weight management services. Your GP can refer you, though waiting lists and availability vary by region. Private prescribing through licensed online prescribers is also available without an NHS referral.
Are prescription weight loss injections safe?
GLP-1 medications like Wegovy and Mounjaro are prescription-only and require clinical assessment. Common side effects include nausea and digestive changes. Serious side effects are rare but possible. Your prescriber will assess suitability based on your health.
Do I need a prescription for weight loss medication?
Yes. All prescription weight loss medications in the UK (Wegovy, Mounjaro, Saxenda) require a prescription from a licensed healthcare professional following a clinical assessment. This ensures the medication is safe and appropriate for you.
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.