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 BMI Is Overweight?
According to NHS guidelines, a BMI of 25.0 to 29.9 is classified as overweight for UK adults. This sits between the healthy weight range (18.5–24.9) and obesity (30.0 and above). Your BMI is calculated using a simple formula based on your weight and height, and it's a useful starting point for understanding your weight health. However, it's important to know that BMI has limitations and doesn't account for muscle mass or where fat is stored. Use our free BMI calculator above to check your personal BMI instantly.
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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 Ranges and Overweight Classification
The NHS BMI categories for UK adults are clearly defined. A BMI of 25.0 to 29.9 puts you in the overweight range, while 18.5 to 24.9 is considered healthy weight. Below 18.5 is underweight, and 30.0 and above is obese.
The BMI formula is straightforward: divide your weight in kilograms by your height in metres squared. For example, someone weighing 75kg and 1.70m tall would have a BMI of approximately 25.9—just into the overweight range.
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS BMI thresholds are lower due to higher health risks at the same BMI. These groups should aim for a healthy BMI of 18.5 to 22.9, with overweight starting at 23.0.
Calculate your exact BMI and see where you fall within these BMI categories UK guidelines using the calculator on this page.
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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.
BMI Limitations and What Else Matters
BMI limitations are important to understand. BMI cannot distinguish between muscle and fat—an athlete with significant muscle mass may have a high BMI but very low body fat. BMI also ignores where fat is stored; fat around the abdomen poses greater health risks than fat elsewhere.
Alongside BMI, the NHS recommends checking your waist circumference. A waist over 94cm (37 inches) in men or 80cm (31.5 inches) in women indicates increased health risk. For Asian adults, these thresholds are lower.
For a complete picture of your health, discuss your BMI alongside your waist measurement, family history, and any existing health conditions with your GP. Our free weight converter helps you track your weight in kg, stone, and lbs—whatever unit feels most natural to you.
- 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.
Is a BMI of 25 overweight?
Yes. According to NHS guidelines, a BMI of 25.0 to 29.9 is classified as overweight. A BMI of exactly 25 is at the lower end of the overweight range. Even a small reduction in weight can move you back into the healthy weight category.
What BMI is healthy weight in the UK?
The NHS defines a healthy BMI as 18.5 to 24.9 for most UK adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9 due to higher health risks at higher BMI levels.
At what BMI do health risks increase?
Health risks begin to increase in the overweight range (BMI 25–29.9) and rise significantly in the obese range (BMI 30 and above). However, other factors like waist circumference, fitness level, and blood pressure also influence your overall health risk.
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, so athletes and very muscular individuals may have high BMI despite low body fat. It also doesn't reflect where fat is stored or other important health markers like blood pressure or cholesterol.
Can I be overweight and still healthy?
Some people in the overweight BMI range remain healthy, especially if they have good fitness levels, healthy blood pressure, and normal blood sugar. However, overweight status does increase health risks on average. Your GP can assess your individual health picture beyond BMI alone.
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.