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
What Is The Normal BMI According To The NHS?
The normal or healthy BMI according to the NHS is between 18.5 and 24.9. BMI (body mass index) is a screening tool that uses your height and weight to estimate whether you're at a healthy weight for your height. However, BMI has limitations — it doesn't account for muscle mass, bone density, or where fat is stored on your body. Use our free BMI calculator above to check your personal BMI instantly and see which category you fall into based on NHS guidelines.
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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 What They Mean
The NHS defines five BMI categories for UK adults. A healthy BMI range starts at 18.5 and goes up to 24.9 — this is the weight range associated with the lowest health risks. Below 18.5 is classified as underweight, which may also carry health risks. The overweight BMI threshold begins at 25.0 and extends to 29.9. Obesity (Class I) spans 30.0 to 34.9, with more severe categories at higher ranges.
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Obese (Class II): BMI 35.0 to 39.9
- Severely obese (Class III): BMI 40.0 and above
These NHS BMI categories apply to most UK adults aged 18 and over. However, the BMI formula and these thresholds have important limitations — they don't distinguish between muscle and fat, so athletic individuals may have a higher BMI without excess body fat.
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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 Guidance, Ethnicity-Adjusted Thresholds, And Next Steps
The NHS also recognises that people of South Asian, Chinese, Black African, and Black Caribbean heritage face higher health risks at lower BMI levels. For these groups, a healthy BMI starts at 18.5 but extends only to 22.9, and the overweight threshold begins at 23.0. This reflects evidence showing these populations have greater risk of type 2 diabetes and cardiovascular disease at the same BMI as other groups.
If your BMI falls outside the healthy range, your GP can provide personalised advice about weight management options. The NHS offers a structured weight management pathway including lifestyle support, behaviour change programmes, and specialist services where appropriate. Use our weight converter to check your weight in different units, and speak with your GP if you'd like to discuss your personal healthy weight range.
- 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.
Is a BMI of 25 considered normal or overweight?
According to NHS guidelines, a BMI of 25.0 falls into the overweight category, not the healthy weight range. The healthy BMI range is 18.5 to 24.9. A BMI of 25 indicates you're just above the threshold. However, BMI is only a screening tool — your GP can assess your overall health, muscle mass, and other factors.
What is the healthy BMI range for UK adults?
The NHS defines a healthy BMI as 18.5 to 24.9 for most UK adults. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is narrower: 18.5 to 22.9. These adjusted thresholds reflect greater health risks in these populations at higher BMI levels.
Why does the NHS have different BMI ranges for different ethnicities?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean heritage develop weight-related health conditions like type 2 diabetes and heart disease at lower BMI levels than other populations. The NHS adjusted its recommendations to reflect this evidence and ensure better health outcomes across all communities.
What should I do if my BMI is above 25?
If your BMI is above 25, speak with your GP. They can assess your individual health, discuss any weight-related concerns, and recommend appropriate support. The NHS offers weight management programmes ranging from self-help resources to specialist services. Even a 5–10% reduction in body weight can bring significant health benefits.
Is BMI accurate for muscular people or athletes?
No. BMI doesn't distinguish between muscle and fat, so muscular or athletic individuals may have a high BMI without excess body fat. Your GP can use additional measurements like waist circumference or body composition assessment to get a fuller picture of your health. BMI is a useful screening tool but has clear limitations.
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.