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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Diet and Nutrition Plan for Weight Loss in the UK
A successful diet and nutrition plan for weight loss combines balanced eating, realistic calorie reduction, and increased physical activity. In the UK, the NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results. For some adults, prescription weight management medication is also available alongside dietary changes. This guide covers evidence-based nutrition strategies and the medication options that may support your weight loss journey if you're eligible.
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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 Prescription Weight Loss Options
If you have 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 may be eligible for prescription weight loss medication in the UK. Three medications are currently licensed for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist given as a once-weekly injection. Clinical trials showed participants lost an average of 15–21% of their body weight.
- Wegovy (semaglutide) — a GLP-1 receptor agonist given as a once-weekly injection, with average weight loss of around 15% in clinical trials.
- Saxenda (liraglutide) — a GLP-1 receptor agonist given as a daily injection.
Prescription weight loss injections work by reducing appetite and supporting you to feel fuller on smaller portions. These medications are prescription-only and require a clinical assessment to determine if they're appropriate for you. They are most effective when used alongside a reduced-calorie diet and increased physical activity — not as a replacement for lifestyle changes.
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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 Treatment
In the UK, you can access prescription weight loss medication through two routes:
- NHS: Referral to a specialist tier 3 weight management service through your GP. Availability varies significantly by region and waiting lists can be lengthy.
- Private: Online consultation with a UK-licensed prescriber followed by dispensing through a registered pharmacy. No NHS referral needed, though costs typically range from £129–£320 per month depending on medication and dose.
Either way, a prescriber will assess your BMI, health history, and any weight-related conditions before issuing a prescription. Start by discussing weight loss options with your GP, who can advise on NHS availability in your area and whether medication is appropriate for you.
- 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 difference between diet alone and diet with prescription weight loss medication?
Diet creates the calorie deficit needed for weight loss, while prescription medication helps reduce hunger and support adherence to that deficit. Medication is most effective when combined with a balanced diet and exercise. For eligible adults, medication can help achieve larger weight loss alongside lifestyle changes.
How much weight can I realistically lose with a nutrition plan?
The NHS recommends aiming for 0.5–1 kg per week, which typically requires a calorie deficit of around 500 kcal daily. Even a 5–10% reduction in body weight can deliver meaningful health benefits including improved blood pressure, blood sugar control, and reduced joint pain.
Can I get weight loss medication on the NHS?
Yes, if you're eligible. You'll need a BMI of 30+ or 27+ with weight-related health conditions, and a referral to a specialist NHS weight management service through your GP. Availability varies by region. Private options are also available without NHS referral.
What should a healthy weight loss diet include?
A balanced weight loss diet should include lean proteins, whole grains, plenty of vegetables and fruit, healthy fats, and limited ultra-processed foods. The NHS Weight Loss Plan recommends eating regularly to avoid overeating, staying hydrated, and reducing sugary drinks and alcohol.
How do I know if I'm eligible for prescription weight loss treatment?
Adults with a BMI of 30 or above, or 27 or above with weight-related conditions (diabetes, hypertension, sleep apnoea, cardiovascular disease), may be eligible. Your GP or a licensed prescriber can assess your individual circumstances and eligibility following a consultation.
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.