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
What's a Good Diet for Weight Loss in the UK?
A good diet for weight loss combines reduced calories with sustainable nutrition and, for some people, prescription weight management support. In the UK, effective weight loss typically involves a calorie deficit of around 500 kcal per day alongside increased physical activity. However, losing weight isn't just about diet—many people find success by combining dietary changes with medical support such as GLP-1 injections or other prescription options if eligible. This guide covers evidence-based nutrition strategies and explores how prescription weight loss medication might fit into your plan.
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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.
Diet, Lifestyle, and Prescription Weight Management Options in the UK
An effective weight loss diet in the UK should focus on sustainable calorie reduction rather than extreme restriction. The NHS recommends losing no more than 0.5 to 1 kg per week for safe, lasting results. A calorie deficit of approximately 500 kcal daily typically achieves this rate.
Evidence-based dietary approaches include the Mediterranean diet (backed by strong cardiovascular evidence), low-carbohydrate eating, intermittent fasting, and simple calorie counting. Choose whichever approach fits your lifestyle—adherence matters more than the specific method.
For many people, prescription weight loss medication has become an important tool. Three medications are UK-licensed for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These GLP-1 and GIP/GLP-1 injections work alongside diet and exercise, helping control appetite and support feeling fuller after smaller meals. Clinical trials showed average weight losses of 15–21% body weight with these medications when combined with lifestyle changes. Our GLP-1 weight loss calculator can help you explore potential results if you're eligible for prescription support.
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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 Access and Eligibility for Prescription Weight Loss
NHS eligibility for prescription weight management includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. You can check your BMI instantly using our free BMI calculator to see where you fall on the NHS scale.
NHS access is through specialist tier 3 weight management services, typically requiring a GP referral. Availability varies significantly by region—waiting lists can be lengthy. Private prescription options are also available through licensed prescribers following online assessment, without NHS referral.
Start by speaking with your GP about your weight loss goals. They can assess whether prescription medication is right for you and discuss whether NHS referral or private options suit your circumstances. Combined with a good diet and regular movement, medication can significantly improve your chances of achieving lasting 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 makes a diet effective for weight loss?
A good weight loss diet creates a calorie deficit (typically 500 kcal per day), focuses on whole foods, includes adequate protein, and is sustainable long-term. The best diet is one you can stick to. The NHS recommends losing 0.5–1 kg per week. Many approaches work—Mediterranean, low-carb, intermittent fasting—so choose what fits your lifestyle.
Can prescription weight loss medication replace diet and exercise?
No. GLP-1 medications like Mounjaro and Wegovy work best alongside dietary changes and increased physical activity. They support appetite control and help you feel fuller, but diet and exercise remain essential. Think of medication as a helpful tool that makes dietary adherence easier, not a replacement for lifestyle changes.
How do I know if I'm eligible for prescription weight loss treatment on the NHS?
You may be eligible if your BMI is 30 or above, or 27 or above with weight-related health conditions like diabetes or high blood pressure. Ask your GP to refer you to your local specialist weight management service, or check your BMI using our free calculator. Eligibility assessment varies by region.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections licensed in the UK for weight management. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist showing average weight losses around 15–21%. Wegovy (semaglutide) is a GLP-1 agonist with average weight losses around 15%. Both require prescription. Your GP or prescriber can discuss which suits you.
Should I wait for NHS treatment or explore private prescription options?
This depends on your circumstances and local NHS availability. NHS services are free but may have long waiting lists. Private prescription options offer faster access but involve costs. Discuss both routes with your GP. Track your progress with our free progress tracker while you arrange treatment.
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.