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
Find Your BMI Weight — NHS Health Guidance
Finding your BMI weight is the first step to understanding whether you're in a healthy weight range according to NHS guidelines. Your BMI (body mass index) is calculated from your height and weight, and the NHS uses it as a screening tool to assess health risk. Using our free BMI calculator above, you can instantly discover your BMI number and see which NHS category you fall into — whether that's healthy weight, overweight, or obese. This guide explains what your result means and what the NHS recommends next.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 BMI categories to classify weight status in UK adults. These categories help your GP identify potential health risks early.
- Underweight: BMI below 18.5 — may indicate nutritional concerns; GP advice recommended
- Healthy weight: BMI 18.5–24.9 — lowest health risk from weight; maintain current habits
- Overweight: BMI 25.0–29.9 — increased risk of weight-related conditions; lifestyle changes may help
- Obese (Class I): BMI 30.0–34.9 — significantly increased health risk; GP discussion recommended
- Obese (Class II): BMI 35.0–39.9 — high health risk; specialist support may be appropriate
- Severely obese (Class III): BMI 40.0+ — very high health risk; urgent GP referral recommended
If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: healthy weight is 18.5–22.9, and overweight starts at 23.0. This is because these populations face higher health risks at lower BMI levels. Use the weight converter on this page to check weights in your preferred units.
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.
When to Seek NHS Support and What Happens Next
If your BMI falls outside the healthy range, your GP can offer support through the NHS weight management pathway. For most people, this starts with self-help tools and community programmes (Tier 1). If you need more support, your GP can refer you to a Tier 3 specialist weight management service, where you may be assessed for prescription weight loss treatment, lifestyle coaching, and medical monitoring.
The NHS also recognises that BMI has limitations — it doesn't account for muscle mass or where fat is stored. Your GP may also measure your waist circumference, as fat around the stomach carries higher health risk. If you have weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea, seeking GP support becomes even more important. Your GP can create a personalised plan based on your individual health.
- 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.
How do I calculate my BMI if I know my weight and height?
Use our free BMI calculator above to enter your height and weight instantly. Or use the formula: divide your weight in kilograms by your height in metres squared. For example, if you weigh 70kg and are 1.75m tall: 70 ÷ (1.75 × 1.75) = BMI of 22.9 (healthy weight). The calculator handles the maths for you.
What's the difference between a healthy BMI and a healthy weight?
A healthy BMI (18.5–24.9) indicates low health risk from weight, but "healthy weight" is personal and depends on your individual health, muscle mass, and medical history. Your GP or a healthcare professional can discuss what weight range is right for you specifically, rather than relying on BMI alone.
Should I be worried if my BMI is in the overweight category?
Not necessarily — overweight BMI (25–29.9) indicates increased risk, but risk varies by individual. Your age, fitness level, family history, and other health conditions all matter. That said, seeking GP advice is sensible if your BMI is consistently above 25, especially if you have other health concerns.
Does the NHS offer weight loss treatment on the NHS?
Yes, through specialist Tier 3 weight management services. Your GP can refer you if you have a BMI of 30 or above, or 27–29.9 with weight-related conditions. Waiting times and availability vary significantly by region. Treatment may include lifestyle support, prescription medications, or other interventions depending on your needs.
Why does the NHS recommend different BMI thresholds for certain ethnic groups?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean heritage develop weight-related health conditions at lower BMI levels than other populations. The NHS adjusted thresholds (healthy weight 18.5–22.9 for these groups) reflect this evidence and ensure fairer, more accurate health screening across all communities.
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.