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 Ways to Weight Loss in the UK
Sustainable weight loss involves a combination of approaches tailored to your individual circumstances. In the UK, adults struggling with excess weight have access to multiple evidence-based methods — from lifestyle changes to prescription weight management medications. If you have a BMI of 30 or above, or a BMI of 27 with weight-related health conditions, prescription medication may be an option worth exploring with your GP. This guide explains the most effective weight loss strategies available to UK adults, including NHS and private pathways to prescription support.
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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.
UK-Licensed Prescription Weight Loss Options
Three prescription medications are currently licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy work as GLP-1 receptor agonists — prescription-only injectables that signal fullness to the brain and may help reduce appetite. Clinical trials showed Mounjaro users lost an average of 15–21% of body weight, while Wegovy users lost approximately 15% on average. Individual results vary significantly, and these medications work best alongside a reduced-calorie diet and increased physical activity.
Eligibility for prescription weight loss medication typically requires a BMI of 30 or above, or BMI 27–29.9 with weight-related conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have access to lower BMI thresholds. Use our free GLP-1 weight loss calculator to explore potential outcomes at different medication doses, and check your BMI using our calculator to understand your starting point.
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 in the UK
NHS access: Weight loss medications are available through specialist tier 3 weight management services, typically accessed via GP referral. However, NHS availability varies significantly by region and waiting lists can be lengthy — sometimes months or years depending on your integrated care board (ICB).
Private access: Prescription weight loss medication is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. This route doesn't require NHS referral and offers faster access, though costs apply (typically £129–£320+ per month depending on dose and dose escalation). Whether you pursue NHS or private pathways, the first step is always a conversation with your GP about whether prescription weight loss treatment is right for you and your health profile.
- 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 weight loss method for me personally?
The best method depends on your BMI, health conditions, preferences, and lifestyle. Start by calculating your BMI using our free calculator, then discuss options with your GP. Sustainable approaches combine dietary changes, physical activity, and potentially prescription support if eligible. Your GP can help tailor a plan to your circumstances.
How much weight can I expect to lose with prescription medication?
Clinical trials showed average weight losses of 15–21% with Mounjaro and approximately 15% with Wegovy — but individual results vary considerably. Some people lose more, some less. Weight loss medications work best alongside a reduced-calorie diet and exercise. Never expect assured outcomes — results depend on many factors including adherence and lifestyle changes.
How do I know if I'm eligible for prescription weight loss medication on the NHS?
You typically need a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions. Eligibility varies by region. Your first step is a conversation with your GP, who can assess your individual circumstances and refer you to specialist services if appropriate. Waiting times vary significantly across the UK.
Can I get weight loss injections privately without seeing my GP first?
Yes, private prescribers can issue prescriptions following an online clinical assessment — no GP referral is required. However, it's still advisable to inform your GP about any prescription medication you're taking. Private access is faster but costs money, whereas NHS access is free but may involve waiting lists.
What lifestyle changes should I make alongside weight loss medication?
The most effective weight loss combines prescription medication with a reduced-calorie diet (typically 500 kcal deficit daily for 0.5 kg weekly loss) and increased physical activity. The NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Consider tracking your progress using our free progress tracker to stay motivated.
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.