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 Meal Plans and Weight Loss Medication in the UK
A structured diet meal plan is most effective for weight loss when combined with lifestyle changes—and for eligible adults, prescription medication can provide additional support. The UK offers several prescription weight management options alongside dietary approaches, helping you achieve sustainable results. Whether you're managing weight through nutrition alone or considering medication, understanding your options and NHS availability is essential for success.
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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.
UK-Licensed Prescription Weight Loss Options
Three main prescription medications are licensed in the UK for weight management alongside diet and exercise: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide).
Mounjaro is a once-weekly injection that works on two hormone pathways (GIP and GLP-1), helping reduce appetite and support feeling fuller after meals. Clinical trials showed average weight loss of approximately 15–21% of body weight when combined with a reduced-calorie diet.
Wegovy is also a once-weekly injection using a single GLP-1 pathway, with average weight loss of around 14.9% of body weight in clinical trials. Saxenda is a daily injection option with slightly lower average weight loss outcomes.
All three are prescription-only medicines requiring assessment by a healthcare professional. Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Use our free BMI calculator above to check where your current weight sits, and our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
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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 Access vs Private Prescribing in the UK
NHS access to prescription weight loss medication is through specialist tier 3 weight management services, typically requiring a GP referral. Availability and waiting times vary significantly by region—some areas have substantial waiting lists. Private access is available through GPhC-registered online prescribers following an online clinical assessment, without needing an NHS referral, though this involves a cost (typically £129–£320 per month depending on medication and dose).
Your GP can assess your eligibility and discuss whether prescription weight loss support is appropriate for you alongside dietary changes. They can also advise whether NHS specialist services are available in your area or whether private prescribing might be an option. Whichever route you take, prescription medication works best as part of a comprehensive approach that includes a structured diet meal plan, regular physical activity, and behaviour change support.
- 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 I use a diet meal plan without medication for weight loss?
Yes, absolutely. Many people successfully lose weight through diet, physical activity, and behaviour change alone. A sustainable approach typically involves a calorie deficit of around 500 kcal per day, which the NHS recommends can result in approximately 0.5–1 kg weight loss per week. Prescription medication is an additional option for eligible adults, not a requirement.
What is the eligibility criteria for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, obstructive sleep apnoea, or cardiovascular disease). If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Your GP or a prescriber can assess your individual eligibility.
How do I access prescription weight loss medication on the NHS?
Ask your GP for a referral to a specialist tier 3 weight management service in your area. These services provide comprehensive assessment and can prescribe weight loss medication alongside dietary and lifestyle support. However, NHS availability and waiting times vary significantly by region. Your GP can advise what's available locally.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) activates one (GLP-1 only). Clinical trials showed Mounjaro achieved average weight loss of 15–21% of body weight, compared to approximately 14.9% for Wegovy. Both are once-weekly injections, prescription-only, and work best alongside a reduced-calorie diet and increased physical activity. Individual results vary considerably.
Should I start a diet meal plan before or after getting prescription weight loss medication?
Both approaches work well. Some people start with diet and lifestyle changes first, then add medication if needed. Others begin medication and diet simultaneously for quicker results. Your GP or prescriber will advise what's most appropriate for your situation. Regardless, successful weight loss combines prescription medication (if prescribed) with dietary changes, physical activity, and behaviour support.
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.