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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BMI Chart — NHS Guidelines for UK Adults
A BMI chart shows where your weight falls on the NHS health scale — helping you understand if you're in a healthy range. The NHS uses BMI (Body Mass Index) as a screening tool to assess health risk, with different categories for different BMI ranges. This guide explains the NHS BMI formula, categories, and what they mean for your health, plus guidance on when to speak to your GP about weight management. Use our free BMI calculator above to find your personal BMI instantly, then use this chart to understand your result.
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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.
NHS BMI Categories and Healthy Weight Ranges
The NHS divides BMI into five main categories based on health risk:
- Underweight (BMI below 18.5) — May indicate health risks; GP advice recommended
- Healthy weight (BMI 18.5–24.9) — Lowest health risk range; maintain current lifestyle
- Overweight (BMI 25.0–29.9) — Increased health risk; lifestyle changes recommended
- Obese Class I (BMI 30.0–34.9) — Significant health risk; GP consultation advised
- Obese Class II (BMI 35.0–39.9) — High health risk; medical support recommended
- Severely obese (BMI 40.0+) — Very high health risk; GP referral important
Remember: BMI is a screening tool and has limitations. It doesn't distinguish between muscle and fat, so athletes may have a high BMI despite low body fat. Your GP can provide personalised context using your BMI range, waist circumference, and overall health profile.
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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 Weight Management Support and When to Seek Help
If your BMI falls outside the healthy range, the NHS offers a structured weight management pathway. Tier 1 includes self-help and digital tools like our free weight converter and BMI calculator. Tier 2 involves your GP and community programmes. Tier 3 provides specialist weight management services, where prescription medications like Mounjaro or Wegovy may be considered. Tier 4 covers bariatric surgery for severe obesity with significant comorbidities.
Contact your GP if your BMI is consistently above 30, if you have weight-related health conditions like type 2 diabetes or high blood pressure, or if you're struggling with weight management. Your GP can assess your individual situation and discuss what support 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 is the healthy BMI range according to the NHS?
The NHS defines healthy weight as a BMI between 18.5 and 24.9. However, for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply — healthy weight is 18.5 to 22.9. Your GP can advise what's healthy for your individual circumstances.
Is BMI the only thing my GP considers when assessing weight?
No. While BMI is a useful screening tool, your GP also considers waist circumference, blood pressure, blood sugar levels, cholesterol, and overall health history. A high BMI doesn't automatically mean poor health, and a normal BMI doesn't assures good health. Context matters.
What should I do if my BMI is in the overweight category?
The NHS recommends lifestyle changes: increase physical activity, reduce calorie intake, and eat a balanced diet. Losing even 5–10% of body weight can improve health markers. If you're struggling, your GP can refer you to a community weight management programme or specialist services.
Can I access weight loss medication through the NHS based on my BMI?
Possibly. If your BMI is 30 or above, or 27–29 with weight-related health conditions, you may be eligible for prescription weight loss treatment through NHS specialist tier 3 services. Eligibility varies by region. Speak to your GP about referral options.
Why are the BMI thresholds lower for some ethnic groups?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean heritage have higher cardiovascular and diabetes risk at lower BMI levels. The NHS adjusted thresholds to better reflect health risk in these populations and ensure earlier intervention where needed.
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.