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 Healthy Range For BMI According To The NHS?
A healthy BMI range according to NHS guidance is between 18.5 and 24.9 for most UK adults. Your BMI (body mass index) is calculated using a simple formula based on your weight and height, and it gives your GP a useful starting point for assessing whether your weight falls within a healthy range for your height. However, BMI is just one health marker — it doesn't account for muscle mass, where fat is stored, or individual health factors. Use our free BMI calculator above to check your personal BMI instantly and see where you fall on the NHS BMI range.
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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 uses five standard BMI categories to classify adult weight ranges in the UK:
- Underweight: BMI below 18.5 — may indicate insufficient nutrition
- Healthy weight: BMI 18.5–24.9 — the target range for most adults
- Overweight: BMI 25.0–29.9 — increased health risks begin to emerge
- Obese (Class I): BMI 30.0–34.9 — significantly increased health risks
- Obese (Class II): BMI 35.0–39.9 — further elevated health risks
- Severely obese (Class III): BMI 40.0 and above — highest health risk category
These BMI categories UK guidelines apply to adults aged 18 and over. For children and teenagers, different age and sex-specific growth reference charts are used. Your GP can help interpret your personal BMI and explain what it means for your health.
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 Guidance For Weight Management And When To Seek Help
The NHS recommends aiming for a healthy BMI through sustainable lifestyle changes: a balanced diet, regular physical activity, and behaviour change support. If your BMI falls into the overweight or obese category, your GP can refer you to NHS weight management services, which operate on a four-tier pathway. Tier 1 offers self-help resources and community programmes; Tier 2 provides primary care-based support; Tier 3 involves specialist multidisciplinary services where prescription weight loss medications may be considered; and Tier 4 covers bariatric (weight loss) surgery for severe obesity with significant health complications. The NHS emphasises that even a 5–10% reduction in body weight can bring meaningful health improvements, so gradual progress is valuable and sustainable.
- 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 number is considered healthy?
According to NHS guidance, a healthy BMI is between 18.5 and 24.9. If you fall within this range, your weight is considered healthy for your height. You can calculate your exact BMI using our free BMI calculator on this page.
Is BMI the same for everyone, or are there different ranges?
For most UK adults, the NHS uses standard BMI thresholds. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: a healthy BMI starts at 18.5 but extends only to 22.9 (not 24.9). This is because these populations face higher cardiovascular and diabetes risk at lower BMI levels.
What are the main limitations of BMI?
BMI has important BMI limitations: it doesn't distinguish between muscle and fat, so athletes may have a high BMI despite low body fat. It also ignores where fat is stored (waist measurement matters), may be inaccurate during pregnancy, and varies in accuracy for elderly individuals. Your GP can assess your overall health beyond BMI alone.
What should I do if my BMI is outside the healthy range?
Speak to your GP, who can discuss your individual circumstances and health goals. If you're overweight or obese, your GP may refer you to NHS weight management services for support, which could include dietary advice, physical activity guidance, behaviour change programmes, or prescription medications if clinically appropriate.
How do I know my healthy weight range for my height?
Calculate your healthy weight range using the BMI formula applied to your height. For a healthy BMI of 18.5–24.9, multiply your height in metres by itself, then multiply by 18.5 and 24.9. Our free BMI calculator instantly shows you this range — just enter your height and it will display the weight range you should aim for.
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.