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
Weight Loss Food and Prescription Medication in the UK
While choosing the right foods is essential for sustainable weight loss in the UK, prescription medications are also available for eligible adults. A combination of balanced nutrition, increased physical activity, and where appropriate, medical support can help with weight management. The NHS recommends a calorie deficit of around 500 kcal per day for gradual, sustainable weight loss. If you're struggling with weight management through diet alone, your GP can discuss whether prescription weight loss options might be suitable for you. Use our free BMI calculator above to check where you currently stand, and discover what support is available.
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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.
Prescription Weight Loss Medication Options in the UK
Three prescription-only GLP-1 medications are licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are not replacements for healthy eating — they work alongside dietary changes and increased physical activity. Clinical trials show that eligible adults may lose between 14–21% of body weight on average, though individual results vary significantly.
- Mounjaro: Dual GIP/GLP-1 injection, 2.5–15 mg weekly, average weight loss ~15–21%
- Wegovy: GLP-1 injection, 0.25–2.4 mg weekly, average weight loss ~15%
- Saxenda: GLP-1 injection, 0.6–3 mg daily, available for several years in the UK
You may be eligible if your BMI is 30 or above, or 27+ with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses if you're considering this option.
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 and Next Steps
NHS access: Referral through your GP to a specialist tier 3 weight management service. Availability and waiting times vary significantly by region (ICB). Private access: Available through GPhC-registered online pharmacies following an online clinical assessment; no NHS referral needed. Both routes require a prescription from a UK-licensed prescriber who will assess your individual suitability.
Start by talking to your GP about your weight loss goals and any underlying health conditions. They can advise whether prescription medication is appropriate for you, or suggest other evidence-based approaches. Sustainable weight loss involves both food choices and, where needed, medical support. Track your progress using our free progress tracker to stay motivated throughout your weight loss journey.
- 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.
Can food choices alone help me lose weight without medication?
Yes. The NHS emphasises that sustainable weight loss comes primarily from a calorie deficit achieved through healthier food choices and increased physical activity. Most people can lose 0.5–1 kg per week through diet and exercise alone. Prescription medications like Mounjaro or Wegovy are additional tools for those who meet eligibility criteria and find weight loss difficult despite dietary effort.
What makes food support weight loss management?
Lower-calorie, nutrient-dense foods (vegetables, lean proteins, whole grains) help create a calorie deficit without excessive hunger. Foods high in fibre and protein promote satiety, reducing overall food intake. The NHS recommends balanced meals rather than restrictive diets for long-term success. A registered dietitian can provide personalised dietary guidance.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if your BMI is 30 kg/m² or above, or 27–29.9 with weight-related conditions (diabetes, high blood pressure, heart disease, sleep apnoea). Some ethnic groups (South Asian, Chinese, Black African, Black Caribbean) have lower BMI thresholds. Only a GP or licensed prescriber can confirm eligibility after clinical assessment.
How do GLP-1 injections work alongside food and exercise?
GLP-1 medications reduce appetite, help you feel fuller after smaller meals, and slow digestion. They are not clinically supported solutions — they support the calorie deficit you create through food choices and activity. Clinical trials show best results when combined with a reduced-calorie diet and increased physical activity. Results vary between individuals.
Where do I start if I want to explore prescription weight loss options?
Speak to your GP first. They can assess your health, discuss whether prescription medication is appropriate, and refer you to NHS specialist services if needed. Alternatively, you can use a private online prescribing service (following clinical assessment). Use our BMI calculator to check your current BMI before your appointment.
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.