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
Understanding Weight and Health — A UK Health Guide
Weight and body composition are complex health topics affected by genetics, medical conditions, lifestyle, and environment. If you're concerned about your health in relation to your weight, you're not alone — around 63% of UK adults are overweight or obese according to NHS data. The good news is that even modest weight loss of 5–10% can bring meaningful health improvements. Understanding your personal BMI, exploring weight management options, and working with your GP are the first steps toward better health. This guide covers what you need to know about weight health in the UK.
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.
What Does BMI Tell You About Your Health?
BMI (body mass index) is a screening tool that estimates whether your weight falls within a healthy range for your height. The NHS uses these categories: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), obese (30.0–34.9), and severely obese (40.0+). However, BMI has important limitations — it doesn't distinguish between muscle and fat, doesn't account for where fat is stored on your body, and may be less accurate for elderly adults or people with significant muscle mass.
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds because these groups face higher health risks at lower BMI levels. Use our free BMI calculator above to check your personal BMI instantly, and remember that your GP can provide personalised health advice based on your individual circumstances.
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.
Health Risks and Weight Management Options in the UK
Being overweight or obese increases your risk of type 2 diabetes, cardiovascular disease, certain cancers, sleep apnoea, and non-alcoholic fatty liver disease. The NHS supports weight management through a four-tier pathway: tier 1 (self-help and digital tools), tier 2 (primary care programmes), tier 3 (specialist weight management services where prescription medications may be available), and tier 4 (bariatric surgery for severe obesity).
If you're interested in exploring weight loss options, speak with your GP about what's available in your area. They can assess your health and discuss approaches ranging from lifestyle changes to referral to specialist services. Our weight converter and progress tracker can help you monitor your weight in the measurements you're comfortable with.
- 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 overweight and obese according to UK health guidance?
According to NHS guidelines, overweight is a BMI of 25.0–29.9, whilst obese is 30.0 and above. These categories help identify health risks, though individual health depends on many factors beyond BMI. Your GP can explain what your specific BMI means for your health.
Can weight loss improve my health even if I don't reach a "healthy" BMI?
Yes. Evidence shows that losing just 5–10% of your body weight can reduce blood pressure, improve blood sugar control, lower cholesterol, reduce joint pain, and decrease your risk of serious health conditions. Sustainable weight loss is often more important than reaching a specific number.
What weight management options are available through the NHS in the UK?
The NHS offers tier 1 support (digital tools and community programmes), tier 2 primary care services, tier 3 specialist weight management services (where prescription medications and structured support are available), and tier 4 bariatric surgery for severe obesity. Access varies by region — ask your GP what's available locally.
Are prescription weight loss medications available on the NHS in the UK?
Prescription weight loss medications like Mounjaro and Wegovy are available through NHS tier 3 specialist weight management services, though availability and waiting times vary significantly by region. Private access is also available through online prescribers following a clinical assessment.
What's a realistic rate of weight loss to aim for?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week for sustainable results. A calorie deficit of about 500 kcal per day typically leads to this rate. Faster weight loss is possible but may increase muscle loss. Your GP or a registered dietitian can provide personalised guidance.
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.