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 Does a BMI of 18.5 to 24.9 Mean?
A BMI between 18.5 and 24.9 is classified as a healthy weight according to NHS guidelines. This range is based on evidence showing that people with a BMI in this bracket have the lowest risk of weight-related health conditions such as type 2 diabetes, heart disease, and certain cancers. However, BMI is just one measure of health — it doesn't account for muscle mass, fitness level, or where fat is stored on your body. Your overall health depends on many factors including diet, physical activity, sleep, and stress levels. Use our free BMI calculator above to check where you fall on the healthy weight scale.
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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 Healthy Weight Guidance and Categories
The NHS healthy weight range is a BMI of 18.5 to 24.9 for most UK adults. This category is associated with the lowest health risks. However, it's important to understand that healthy weight isn't the same for everyone — it depends on your age, ethnicity, muscle mass, and overall fitness.
- BMI 18.5–24.9: Healthy weight (lowest disease risk)
- BMI 25.0–29.9: Overweight (increased health risks)
- BMI 30.0+: Obese (significantly increased health risks)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy BMI starts at 18.5 but peaks at 22.9 rather than 24.9. This is because these populations face higher risks of type 2 diabetes and heart disease at the same BMI levels as other groups. Your GP can discuss what a healthy weight means specifically for you based on your individual health profile and medical history.
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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.
Maintaining a Healthy Weight in the UK
If your BMI falls within the 18.5–24.9 range, maintaining your current weight involves consistent healthy habits rather than strict dieting. The NHS recommends a balanced diet rich in vegetables, fruits, whole grains, and lean proteins, combined with at least 150 minutes of moderate physical activity each week. Small, sustainable changes — like taking the stairs, walking short distances, or cooking at home more often — are far more effective than extreme approaches.
If you're struggling to maintain your weight or want personalised UK health guidance, your GP or a registered dietitian can provide evidence-based support. Use our free weight converter and progress tracker to monitor your weight consistency over time and ensure you stay within the healthy 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 18.5–24.9 healthy for everyone?
A BMI in this range is considered healthy for most UK adults according to NHS guidelines. However, ethnicity matters — people of South Asian, Chinese, Black African, or Black Caribbean heritage have different risk thresholds and may be healthier at a BMI of 18.5–22.9. Additionally, very muscular individuals or athletes may have a BMI above 25 but still be healthy. Your GP can assess your personal health context.
What's the difference between healthy weight and ideal weight?
Healthy weight refers to the BMI range associated with lowest disease risk (18.5–24.9). Ideal weight is more personal and varies based on your frame size, muscle mass, genetics, and individual goals. You can be within the healthy weight range but feel or perform better at a different weight within that range.
How do I calculate my BMI to see if I'm in the 18.5–24.9 range?
BMI is calculated by dividing your weight in kilograms by your height in metres squared (BMI = kg ÷ m²). Our free BMI calculator on this page does this instantly — just enter your weight and height. It will tell you exactly where you fall on the NHS scale and what category you're in.
Can I lose weight if my BMI is already 18.5–24.9?
Yes, you can lose weight safely if your BMI is in the healthy range, though rapid loss isn't necessary. The NHS recommends losing no more than 0.5–1 kg per week. If you're considering weight loss, discuss your goals with your GP to ensure it's appropriate for your health and not driven by appearance alone.
What should I do if my BMI is just above 24.9?
If your BMI is 25–29.9 (overweight category), the NHS recommends lifestyle changes including balanced nutrition and regular physical activity. Even a 5–10% reduction in body weight can improve blood pressure, blood sugar, and cholesterol. Your GP can provide personalised advice about whether weight loss is necessary for your health.
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.