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
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Body Index Weight Chart — Your UK Health Reference
A body index weight chart helps you understand where your current weight falls on the health spectrum. In the UK, we use the Body Mass Index (BMI) — a measurement based on your height and weight — to assess whether you're at a healthy weight, overweight, or obese. NHS guidance divides adults into five BMI categories, with different thresholds for people of South Asian, Chinese, Black African, or Black Caribbean heritage. This guide explains how to read a weight chart, what the categories mean, and how to use this information to make informed health decisions with your GP.
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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.
Understanding UK BMI Categories and Weight Ranges
The NHS uses five BMI categories to classify adult weight:
- Underweight: BMI below 18.5 — may need nutritional support
- Healthy weight: BMI 18.5–24.9 — lowest risk of weight-related disease
- Overweight: BMI 25–29.9 — increased health risk, especially with comorbidities
- Obese (Class I): BMI 30–34.9 — significantly elevated health risk
- Obese (Class II): BMI 35–39.9 — high health risk
- Severely obese (Class III): BMI 40+ — very high health risk
For South Asian, Chinese, Black African, and Black Caribbean adults, the NHS recommends lower thresholds because these populations face higher risk of type 2 diabetes and cardiovascular disease at the same BMI levels. For these groups, the healthy weight range is BMI 18.5–22.9, and overweight starts at 23. Our free BMI calculator on this page automatically assesses your category against NHS guidance, so you can see exactly where you stand.
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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.
How to Use a Weight Chart and Take Action
To use a weight chart, find your height on the left axis and your weight on the bottom, then locate where they meet. Your BMI is shown in the corresponding colour — green for healthy, yellow for overweight, orange for obese, red for severely obese. If your BMI falls outside the healthy range, the next step is to discuss weight management options with your GP. This might include lifestyle changes such as reducing calorie intake or increasing physical activity, or — if you meet NHS eligibility criteria — prescription weight loss support. You can use our free weight converter to switch between kg, stone, and pounds, and our GLP-1 weight loss calculator to explore potential outcomes if medication is right for you. Remember: individual results vary, and any changes to your health routine should be discussed with your healthcare provider first.
- 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 "body index" mean?
Body index refers to your Body Mass Index (BMI) — a calculation based on your height and weight. It's used to screen for weight categories and associated health risks. BMI is useful but has limitations — it doesn't account for muscle mass, bone density, or where fat is stored, so your GP may also consider other measurements like waist circumference.
Is the weight chart the same in the UK as other countries?
The BMI categories are the same globally, but the UK uses slightly different thresholds for certain populations. The NHS recommends lower BMI boundaries for South Asian, Chinese, Black African, and Black Caribbean adults due to higher disease risk at lower BMI levels. Always use UK NHS guidance as your reference.
What should I do if my BMI is in the overweight range?
If your BMI is 25–29.9, you're in the overweight category. The first step is to speak with your GP. Losing even 5–10% of your body weight can improve health markers like blood pressure and blood sugar. Your GP can advise on nutrition, physical activity, and whether weight management support is appropriate for you.
Can I use a weight chart if I'm pregnant or very muscular?
BMI is less accurate during pregnancy and for very muscular individuals (including athletes), because it doesn't distinguish between muscle and fat. If you're pregnant, ask your midwife or GP for personalised weight guidance. If you're very muscular, your GP can assess your health using other methods alongside BMI.
How often should I check my weight chart?
The NHS recommends checking your weight regularly — typically weekly or monthly — as part of a structured weight management plan. Weighing yourself too frequently (daily) can be misleading due to normal water retention and digestive fluctuations. Consistency matters more than frequency.
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.