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
Good Diets For Weight Loss in the UK
Finding the right diet for weight loss depends on what works for your lifestyle and health goals. In the UK, effective weight management combines sustainable dietary changes with support from your GP or healthcare team. This guide covers evidence-based diets, prescription options like GLP-1 injections, and how to work out what suits you best. Whether you're looking for NHS weight loss support or exploring medication eligibility, understanding your options is the first step toward meaningful, lasting weight management.
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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.
Evidence-Based Diets and Prescription Weight Management Options in the UK
The most effective diets for weight loss in the UK combine a calorie deficit with sustainable eating patterns. The NHS recommends losing 0.5–1 kg per week for safe, lasting results. Popular evidence-backed approaches include:
- Mediterranean diet — emphasises vegetables, fish, olive oil, and whole grains; strong evidence for cardiovascular health and sustainable weight management
- Low-carbohydrate diet — effective short-term, though long-term results are similar to standard calorie restriction
- Intermittent fasting — patterns like 16:8 or 5:2 can support a calorie deficit for some people
- Weight loss medication — for eligible adults, prescription GLP-1 injections like Mounjaro (tirzepatide), Wegovy (semaglutide), or Saxenda (liraglutide) are available alongside diet and activity changes
For prescription weight loss options, UK eligibility typically includes a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses if you're considering medication.
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 Support Versus Private Prescription Weight Management in the UK
If you're interested in prescription weight management, your GP can discuss whether you're eligible and refer you to your local NHS specialist weight management service (tier 3). However, NHS availability varies significantly by region and waiting lists can be lengthy. Private online prescribing is an alternative for eligible adults — you'll have a clinical assessment with a UK-licensed prescriber, and if appropriate, a prescription is issued by a GPhC-registered pharmacy. Whichever route you choose, weight loss medications work best alongside dietary changes and increased physical activity. Calculate your current BMI using our free BMI calculator to see where you sit on NHS guidelines, then have a conversation with your GP about your options and what approach suits your situation.
- 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 diet for weight loss in the UK?
The best diet is one you can sustain long-term. Evidence supports Mediterranean, low-carb, and calorie-restricted approaches — all achieve similar weight loss when a calorie deficit is maintained. The NHS recommends losing 0.5–1 kg per week. Choose based on what fits your lifestyle and preferences, and consider support from a GP or dietitian.
How do GLP-1 weight loss injections work alongside diet?
GLP-1 medications like Mounjaro and Wegovy support appetite control and feeling fuller after meals, but they are most effective combined with a reduced-calorie diet and increased physical activity. They're not a substitute for lifestyle changes — think of them as a tool that makes dietary changes easier to stick to.
Am I eligible for prescription weight loss medication on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27+ with weight-related conditions like type 2 diabetes or high blood pressure. Referral is through your GP to a specialist tier 3 weight management service. Availability varies by region, and waiting lists can be long. Your GP can assess your eligibility.
What's the difference between NHS and private weight loss medication?
NHS prescribing is through specialist services (often with waiting lists), while private online prescribing is available without NHS referral if clinically appropriate. Both require a prescription from a licensed UK prescriber and work best alongside diet and activity. Private options are available sooner but involve out-of-pocket costs.
How much weight can I expect to lose with diet and medication combined?
Results vary significantly. With diet alone, 0.5–1 kg per week is sustainable. Clinical trials of GLP-1 medications showed average weight losses of 15–21% over time when combined with dietary changes. Individual results depend on starting weight, adherence, and personal metabolism. Use our weight loss calculator to explore projections.
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.