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 Weight Really Means for Your Health
Weight is more than just a number on the scales — it's a key indicator of your overall health and wellbeing. In the UK, weight management is guided by NHS standards that take into account your height, age, and individual health circumstances. Understanding what constitutes a healthy weight for you personally, and how weight relates to conditions like type 2 diabetes and heart disease, is the foundation of making informed health decisions. This guide explains how to assess your weight in a UK context, what the NHS recommends, and how you can use simple tools to understand your personal health profile.
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.
How the NHS Defines Healthy Weight
The NHS uses BMI (Body Mass Index) as the primary screening tool to categorise healthy weight. A healthy BMI for most UK adults is between 18.5 and 24.9. Use our free BMI calculator on this page to check your personal BMI instantly. BMI is calculated by dividing your weight in kilograms by your height in metres squared. However, it's important to understand that BMI has limitations — it does not distinguish between muscle and fat, so athletes or very muscular individuals may have a higher BMI despite being in good health. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds, with a healthy range of 18.5 to 22.9, because these groups face higher cardiovascular and diabetes risk at the same BMI levels. Beyond BMI, the NHS also considers waist circumference — for men, above 94cm (37 inches) indicates increased health risk, and above 102cm (40 inches) indicates high risk. For women, the thresholds are 80cm (31.5 inches) for increased risk and 88cm (34.5 inches) for high risk.
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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.
Weight Categories and What They Mean
The NHS categorises weight into clear bands. A BMI below 18.5 is underweight; 18.5–24.9 is healthy weight; 25.0–29.9 is overweight; 30.0–34.9 is obese (Class I); 35.0–39.9 is obese (Class II); and 40.0 and above is severely obese (Class III). Each category carries different health implications. Being overweight or obese increases your risk of type 2 diabetes, high blood pressure, certain cancers, sleep apnoea, and cardiovascular disease. Conversely, even modest weight loss — as little as 5–10% of your body weight — can significantly improve these health markers. Convert your weight between kg, stone, and pounds using our free weight converter to easily understand where you fall on these scales.
- 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 a healthy weight for my height?
Your healthy weight range depends on your height and BMI. Use our free BMI calculator above to find your personal healthy weight range. For example, at 5ft 8in (173cm), a healthy weight is approximately 55–74kg (8st 10lbs to 11st 10lbs). For South Asian or Black African adults, the range may be slightly lower. Your GP can provide personalised guidance based on your individual health factors.
Is weight the only indicator of health?
No. While weight is important, other factors matter too. Waist circumference, blood pressure, cholesterol, blood sugar levels, and fitness all contribute to your overall health. Someone with a healthy BMI but high waist circumference may still have increased health risks. This is why NHS weight management is holistic — it considers multiple health markers, not just the number on the scales.
What's the difference between BMI and body fat percentage?
BMI is a screening tool based on height and weight only. Body fat percentage measures the actual proportion of fat in your body. BMI does not distinguish between muscle and fat — a muscular person may have a high BMI but low body fat. Body fat percentage gives a more complete picture but is harder to measure accurately outside clinical settings. Both can be useful alongside other health assessments.
How quickly should I lose weight if I'm overweight?
The NHS recommends losing weight at a rate of 0.5–1kg (1–2lbs) per week for sustainable results. This typically requires a calorie deficit of around 500 calories per day. Faster weight loss may lead to muscle loss and is harder to maintain long-term. Your GP can advise on safe weight loss strategies for your individual circumstances, which may include dietary changes, increased physical activity, or prescription weight management medications.
Can I access weight loss support through the NHS?
Yes. The NHS offers a tiered weight management pathway. Tier 1 includes self-help and community programmes like the NHS Weight Loss Plan. Tier 2 includes primary care support. Tier 3 includes specialist multidisciplinary weight management services where prescription medications may be considered. Access varies by region. Speak to your GP about available options in your area or try our GLP-1 weight loss calculator to explore potential treatment options.
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.