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 A Normal BMI Range According To The NHS?
A normal or healthy BMI range is between 18.5 and 24.9, according to NHS guidance. BMI (body mass index) is a simple screening tool that estimates whether your weight is healthy for your height. However, it's important to understand that BMI has limitations — it doesn't distinguish between muscle and fat, and different ethnic groups have different risk thresholds. Our free BMI calculator above can help you find your personal BMI instantly and see where you fall on the NHS 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 BMI Categories And What They Mean
The NHS divides BMI into five clear categories to help you understand your weight status:
- Underweight (BMI below 18.5): May indicate insufficient nutrition or other health concerns — speak to your GP if your BMI is persistently low.
- Healthy weight (BMI 18.5–24.9): This is the target range associated with the lowest risk of weight-related health problems.
- Overweight (BMI 25.0–29.9): Increased risk of conditions like type 2 diabetes and high blood pressure, but not yet in the obese category.
- Obese Class I (BMI 30.0–34.9): Significantly elevated health risks; weight management is strongly recommended.
- Obese Class II (BMI 35.0–39.9): High health risks; specialist weight management support may be beneficial.
- Severely obese (BMI 40.0+): Very high risk of serious health complications; referral to NHS specialist services is typically recommended.
These NHS categories apply to most UK adults of European descent. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, your risk at lower BMI levels is higher, so the NHS recommends lower thresholds: healthy weight becomes 18.5–22.9, and overweight starts at 23.0.
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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 into the overweight or obese range, the NHS offers a structured weight management pathway. Tier 1 begins with self-help tools and community programmes — MyWeightCheck's free tools, including the weight converter and BMI calculator, can support you here. Tier 2 involves your GP, who may refer you to a behaviour change programme. Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss medication may be considered if your BMI is 30+ (or 27.5+ with weight-related health conditions). Always speak to your GP about your BMI results — they can assess your individual risk and recommend the right support 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 BMI formula used by the NHS?
The NHS uses the standard BMI formula: weight in kilograms divided by height in metres squared. For example, if you weigh 70kg and are 1.75m tall, your BMI is 70 ÷ (1.75 × 1.75) = 22.9. You can calculate this instantly using our free BMI calculator above.
Why are BMI limitations important to understand?
BMI doesn't distinguish between muscle and fat — a muscular athlete may have a high BMI but low body fat percentage. BMI also ignores where fat is stored; waist circumference is equally important. The NHS acknowledges these limitations, which is why your GP considers your full health picture, not just your BMI number.
Is a BMI of 25 overweight according to NHS guidance?
Yes, a BMI of 25.0–29.9 falls into the NHS overweight category for most UK adults. However, this doesn't mean you need to panic — the NHS recommends gradual lifestyle changes like increased physical activity and modest dietary adjustments. Your GP can advise whether weight loss is appropriate for your individual health.
Do children use the same BMI categories as adults?
No, children's BMI is calculated differently using age and sex-specific centile charts from the UK90 growth reference. Adult BMI categories don't apply to under-18s. If you're concerned about a child's weight, ask your GP or health visitor for guidance specific to their age.
When should I ask my GP about my BMI?
Contact your GP if your BMI is consistently below 18.5 or above 30, or if you have a BMI between 25–29.9 with health conditions like high blood pressure or type 2 diabetes. Your GP can assess your individual risk factors and discuss weight management options, including whether specialist referral or prescription medication support might help.
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.