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 in the UK
Obesity is a significant health concern in the UK, affecting around 28% of adults. A BMI of 30 or above is classified as obese according to NHS guidelines, though lower thresholds apply for people of South Asian, Chinese, Black African, and Black Caribbean heritage. Understanding what obesity means for your health and the support available can help you make informed decisions about your wellbeing. This guide covers the health context, what being obese means, and the practical steps available through the NHS and other pathways.
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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.
Health Risks Linked to Obesity
Excess weight significantly increases the risk of serious health conditions. According to NHS data, obesity is linked to approximately 1 in 13 deaths in the UK. People living with obesity have substantially higher risks of:
- Type 2 diabetes — up to 80 times higher risk at severe obesity levels
- Heart disease and stroke — excess weight increases blood pressure and affects cholesterol levels
- Certain cancers — 13 cancer types are linked to excess weight, including bowel, breast, and endometrial cancers
- Obstructive sleep apnoea — disrupts breathing during sleep and affects oxygen levels
- Osteoarthritis — excess weight puts pressure on joints, particularly knees and hips
- Non-alcoholic fatty liver disease — fat accumulation in the liver affects its function
The good news is that even modest weight loss — as little as 5–10% of body weight — can significantly improve these health outcomes and reduce disease risk. Your GP can assess your individual health risks and discuss personalised options.
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 Support & Treatment Options Available
The NHS offers a structured pathway for weight management support. Tier 1 support includes digital tools and community programmes available to anyone. Tier 2 involves primary care-based behaviour change support through your GP. Tier 3 means referral to specialist multidisciplinary weight management services, where prescription weight loss medications may be considered for eligible adults.
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or hypertension, may be eligible for prescription treatment. Options include GLP-1 medications alongside lifestyle changes. You can also use our free BMI calculator above to check your current BMI and explore your personal health context. Speak with your GP about which pathway is right for you.
- 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 is considered obese in the UK?
According to NHS guidelines, a BMI of 30 or above is classified as obese. However, people of South Asian, Chinese, Black African, or Black Caribbean heritage have lower risk thresholds — the NHS recommends a BMI of 27.5 or above be assessed as obese for these groups due to higher health risks at lower weights.
Am I overweight or obese?
A healthy BMI according to the NHS is 18.5 to 24.9. A BMI of 25 to 29.9 is classified as overweight, and 30 or above is obese. Use our free BMI calculator on this page to check your personal BMI instantly and understand where you fall on the NHS scale.
What health conditions are linked to obesity?
Obesity significantly increases risk of type 2 diabetes, heart disease, stroke, certain cancers, sleep apnoea, osteoarthritis, and fatty liver disease. Even a 5–10% reduction in body weight can meaningfully improve these health outcomes and reduce disease risk.
How can the NHS help with weight management?
The NHS provides a structured four-tier pathway. Your GP can refer you to tier 2 or tier 3 services, which may include behaviour change support, dietitian advice, and prescription medications for eligible adults. Availability varies by region — speak with your GP about local options.
What weight loss medications are available in the UK?
GLP-1 receptor agonist medications such as Wegovy and tirzepatide (Mounjaro) are prescription-only and available through NHS specialist services or private prescribing following clinical assessment. These are used alongside lifestyle changes, not as a replacement for them. Try our GLP-1 weight loss calculator to explore potential outcomes.
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.