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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What to Eat for Weight Loss: UK Medication & Diet Guide
When it comes to weight loss, what you eat matters — but so does understanding all the options available to you in the UK. Alongside dietary changes, prescription weight management medications like Mounjaro and Wegovy have become available to eligible adults through the NHS and private prescribing. This guide explains the diet fundamentals and the medication options that can support your weight management journey, helping you understand what approaches might work for your circumstances.
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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-Licensed Weight Loss Medications: Options and Eligibility
Three prescription-only weight loss medications are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All are GLP-1 receptor agonists (or in Mounjaro's case, a dual GIP/GLP-1 agonist) that work by reducing appetite and helping you feel fuller after smaller meals.
You may be eligible for prescription weight loss medication if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply.
In clinical trials, Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy supported losses of around 15% — though individual results vary significantly. These medications are prescription-only and require a clinical assessment before being prescribed.
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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 vs Private Access: How to Find Out If You're Eligible
In the UK, you can access prescription weight loss medication through NHS specialist weight management services or via private online prescribing. NHS access is typically through a referral from your GP to a tier 3 specialist service, though availability and waiting times vary significantly by region. If you'd like to explore your options, speak with your GP about whether prescription weight loss treatment could support your weight management journey.
Privately, you can have an online consultation with a UK-licensed prescriber following a clinical assessment. Costs vary by dose and provider. Either way, weight loss medications work best alongside a reduced-calorie diet and increased physical activity — they're not a substitute for lifestyle changes. Calculate your current BMI using our free tool to help you understand where you stand, and use our GLP-1 weight loss calculator to explore potential outcomes if you become eligible for medication.
- 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 should I eat if I'm taking weight loss medication?
Focus on whole foods: lean proteins, vegetables, fruits, and whole grains. Eat slowly and in smaller portions — weight loss medications help with appetite, not what you choose to eat. Avoid sugary drinks and processed foods. Your prescriber may also refer you to a dietitian for personalised guidance.
Can I lose weight without medication in the UK?
Yes. The NHS recommends starting with a reduced-calorie diet (around 500 kcal deficit daily for 0.5 kg/week loss) and increased physical activity. Tier 1 and 2 NHS services offer free support through digital tools and community programmes. Medication is only one option for eligible adults.
How do I know if I'm eligible for weight loss medication on the NHS?
Generally, a BMI of 30 or above, or 27–29.9 with health conditions like diabetes. Speak with your GP, who can refer you to a specialist weight management service for assessment. Eligibility varies by region and individual health factors.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP/GLP-1 agonist (once-weekly, doses up to 15 mg); Wegovy is a GLP-1-only agonist (once-weekly, max 2.4 mg). Clinical trials suggest Mounjaro may produce slightly higher average weight loss, but individual results vary. Both require prescription.
How long does weight loss take with prescription medication?
Weight loss is gradual. Most people start noticing changes after 4–8 weeks, with significant loss typically over 3–6 months. The NHS recommends losing 0.5–1 kg per week for sustainable results. Medication works best alongside diet and activity changes.
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.