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
Fat Weight Loss Diet Plan: UK Medication & NHS Options
A sustainable fat weight loss diet plan combines dietary changes with lifestyle improvements, and for eligible adults, prescription medication can provide additional support. In the UK, weight management has become more accessible through both NHS services and prescription options like Mounjaro and Wegovy. This guide explores how diet, exercise, and medical support work together, plus how to find out if you're eligible for prescription weight loss medication through your GP or private prescriber.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections, whilst Saxenda is a daily injection. In clinical trials, these medications helped participants lose an average of 15–21% of their body weight when combined with a reduced-calorie diet and increased physical activity. You may be eligible if you have a BMI of 30 or above, or 27 or above with a weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. These are prescription-only medicines requiring a clinical assessment before being prescribed. Our GLP-1 weight loss calculator can help you estimate potential weight loss at different doses, and our BMI calculator will show your current weight management category.
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 Access vs Private Prescribing in the UK
The NHS provides weight management support through specialist tier 3 services, though availability varies significantly by region and waiting lists can be lengthy. Your GP can refer you to a local specialist weight management service if you meet criteria. Alternatively, prescription weight loss medication is available through private online prescribers following a clinical assessment—many adults choose this route for faster access. Both routes require a thorough health check. A successful weight loss plan includes a calorie deficit (typically 500 kcal per day for around 0.5 kg per week loss), increased physical activity, and behaviour change support. Track your progress with our free progress tracker to stay motivated and monitor results over time.
- 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 get weight loss medication on the NHS?
Yes, if you meet eligibility criteria. Your GP can refer you to a specialist weight management service. NICE has approved tirzepatide (Mounjaro) for NHS use. However, waiting lists vary by region—some areas have significant delays. Ask your GP about local availability and whether you qualify for tier 3 specialist services.
What is the best diet plan for weight loss in the UK?
The most effective plan is one you can sustain long-term. A calorie deficit of around 500 kcal daily typically results in 0.5 kg weekly loss. The Mediterranean diet has strong evidence for cardiovascular health. Low-carb, intermittent fasting, and balanced calorie restriction all work—choose whichever fits your lifestyle best.
How much weight can I lose with Mounjaro or Wegovy?
Clinical trials show average weight loss of 15–21% of body weight over 68 weeks when combined with diet and exercise. Individual results vary significantly. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses based on your starting weight.
What is the eligibility criteria for weight loss injections in the UK?
You may be eligible if you have a BMI of 30 or above, or 27 or above with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, heart disease). South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds. A prescriber will assess your individual circumstances.
How do I know if I'm overweight according to NHS guidance?
Use our free BMI calculator to check your personal BMI instantly. The NHS defines healthy weight as a BMI of 18.5–24.9. A BMI of 25–29.9 is overweight, and 30 or above is obese. Our weight converter can help you understand your weight in stone, pounds, and kilograms across different units.
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.