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 Obesity Charts and Health Risks in the UK
An obesity chart helps you understand where your weight falls on the health spectrum and what health risks may be associated with excess weight. In the UK, obesity is defined as a BMI of 30 or above, though thresholds differ for people of South Asian, Chinese, Black African, and Black Caribbean heritage. Being aware of your BMI category is an important first step in understanding your health. Use our free BMI calculator above to find your personal BMI instantly, then read on to discover what the evidence tells us about obesity and health.
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.
Health Conditions Linked to Excess Weight
Excess weight significantly increases the risk of serious health conditions. People with obesity are at substantially higher risk of type 2 diabetes — up to 80 times higher at severe obesity levels. Research shows strong links between obesity and cardiovascular disease, including high blood pressure, heart attack, and stroke. Obesity is also linked to at least 13 types of cancer, including breast, bowel, and endometrial cancer. Other conditions associated with excess weight include obstructive sleep apnoea, non-alcoholic fatty liver disease, osteoarthritis, and reproductive issues. Even modest weight gain increases risk; conversely, losing just 5–10% of body weight can meaningfully reduce these risks and improve blood sugar control, blood pressure, and cholesterol levels.
- Type 2 diabetes risk increases significantly with BMI
- Cardiovascular disease becomes more common in obese individuals
- Certain cancers are more prevalent in people with excess weight
- Joint problems and sleep disorders are more likely with higher BMI
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.
Support Available and Next Steps
The NHS recognises obesity as a serious health issue and provides support through a tiered weight management pathway. Your GP can assess your health, discuss weight management options, and refer you to specialist services if appropriate. For many people, sustainable lifestyle changes — including dietary adjustment and increased physical activity — form the foundation of weight management. For eligible adults, prescription weight loss options may be available through NHS specialist services or private prescription. Our GLP-1 weight loss calculator can help you understand potential outcomes if you're considering medication options. Remember that weight is influenced by many factors including genetics, medical conditions, and environment — judgement-free support is always available from your healthcare team.
- 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 BMI counts as obesity according to UK guidelines?
According to NHS guidelines, a BMI of 30 or above is classified as obese. For South Asian, Chinese, Black African, and Black Caribbean adults, the threshold is lower at 27.5 or above, because these groups have higher health risks at lower BMI levels. You can calculate your personal BMI instantly using our free BMI calculator.
What are the main health risks of obesity?
Excess weight increases risk of type 2 diabetes (significantly), cardiovascular disease, certain cancers, sleep apnoea, fatty liver disease, and osteoarthritis. Even a 5–clinically studied weight loss can reduce these risks meaningfully and improve blood pressure and cholesterol.
How much weight do I need to lose to see health benefits?
Evidence shows that losing even 5–10% of your body weight produces measurable health improvements, including better blood sugar control and lower blood pressure. You don't need to reach a "perfect" weight to see benefits — gradual, sustainable loss is most effective.
What's the difference between overweight and obese according to the obesity chart?
According to UK health charts, "overweight" is a BMI of 25–29.9, while "obese" is BMI 30 or above. An obese BMI indicates higher health risks than overweight, though both carry increased risk compared to a healthy weight range of 18.5–24.9.
Where can I get support for weight management on the NHS?
Start by speaking with your GP, who can discuss your health and weight management options. The NHS provides a tiered pathway including self-help resources, community programmes, and specialist weight management services. Your GP can refer you to appropriate services and discuss all available options including lifestyle support and prescription treatments for eligible adults.
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.