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 NBMI? UK Health Information
NBMI refers to updated or alternative BMI assessment approaches used in UK health guidance. The NHS uses BMI as a key screening tool for weight-related health risks, but recognises that BMI alone does not tell the complete health picture. This UK health guide explains how BMI assessment works, why the NHS uses it alongside other measurements, and what it means for your weight management journey. Understanding BMI in context helps you make informed decisions about your health.
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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.
How BMI Assessment Works in the NHS
BMI (Body Mass Index) is calculated using your height and weight: weight in kg divided by height in metres squared. The NHS uses BMI as a screening tool because it correlates with health risk across populations.
UK health guidance recognises that BMI has limitations. It does not distinguish between muscle and fat, does not account for where fat is stored on your body, and may not be accurate for very muscular individuals, elderly adults, or during pregnancy.
- NHS healthy weight BMI range: 18.5 to 24.9
- For South Asian, Chinese, Black African, and Black Caribbean adults: 18.5 to 22.9 (lower thresholds due to higher cardiovascular risk)
- Waist circumference also matters—measure around your natural waist for additional health context
Our free BMI calculator uses NHS guidelines to assess your weight category instantly with UK measurements.
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.
Eligibility for Weight Management Support
If your BMI or waist measurement suggests increased health risk, you may be eligible for NHS weight management support or prescription treatment. The NHS classifies eligibility in tiers.
- Tier 1: Self-help, digital tools, and community programmes—available to anyone
- Tier 2: Primary care behaviour change support—referral from your GP
- Tier 3: Specialist weight management services—where prescription medications may be offered
- Tier 4: Specialist bariatric surgery services—for severe obesity with comorbidities
Speak with your GP about weight management options. Eligibility varies by region, and waiting lists differ across the UK. Our free weight converter and healthy weight guide help you understand where you sit relative to NHS health advice.
- 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 does NBMI stand for in UK health?
NBMI typically refers to BMI assessment or newer BMI guidance frameworks. The NHS uses BMI as a primary screening tool for weight-related health risk, alongside waist circumference and other clinical measures. BMI alone is not diagnostic—your GP considers your full health picture.
What's the healthy BMI range according to NHS guidance?
For most UK adults, a healthy BMI is 18.5 to 24.9. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends 18.5 to 22.9, as these groups face higher cardiovascular risk at standard BMI levels. Use our free BMI calculator for your personal assessment.
Why does the NHS use different BMI thresholds for some ethnic groups?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean descent have higher risk of type 2 diabetes and heart disease at lower BMI levels. The NHS adjusted thresholds to better reflect actual health risk and ensure equitable care across all communities.
Can I access weight management treatment through the NHS?
Yes. Weight management is available through NHS specialist tier 3 services following referral from your GP. Access and waiting times vary by region (ICB). Your GP can assess your eligibility and refer you if appropriate. Private prescribing is also available through licensed UK providers.
What should I do if I'm concerned about my weight?
Speak with your GP, who can assess your individual health risk, consider your medical history, and recommend appropriate support—whether that's lifestyle changes, behaviour change programmes, or specialist services. MyWeightCheck provides free calculators and UK health information to help you understand your starting point.
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.