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
How Heavy — Understanding Weight & Health in the UK
"How heavy" is a common question people ask about their own weight or when comparing to others, but weight alone doesn't tell the full health story. In UK health guidance, weight is measured in kilograms (kg), stone, or pounds (lbs), and what matters most is how your weight relates to your height, age, and individual health conditions. The NHS uses BMI (body mass index) as a screening tool to assess whether weight falls into a healthy range. However, weight is influenced by many factors including genetics, metabolism, muscle mass, and medical conditions — so understanding your weight in health context is more useful than a number alone.
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.
Weight Measurement & UK Health Context
In the UK, weight is typically measured in stone and pounds (st and lbs) in everyday conversation, though the NHS uses kilograms (kg) for clinical measurements. Understanding your weight in both systems can be helpful.
- 1 stone = 14 pounds (lbs) exactly
- 1 kg = 2.20462 lbs
- 1 stone = 6.35029 kg
Use our free weight converter above to switch between kg, stone, and lbs instantly. According to NHS guidance, a healthy weight range depends on your height. For example, an adult who is 5ft 8in (173cm) tall would have a healthy weight range of approximately 55–74 kg (8st 10lbs to 11st 10lbs). Your GP can provide personalised advice about what a healthy weight means for your specific health profile, especially if you have weight-related health conditions like type 2 diabetes or high blood pressure.
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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 & Health Weight Assessment
The NHS uses BMI (body mass index) to screen whether weight falls into a healthy range, calculated by dividing weight in kilograms by height in metres squared. A healthy BMI is 18.5–24.9 according to NHS guidelines, though people of South Asian, Chinese, Black African, or Black Caribbean heritage have lower recommended thresholds (18.5–22.9).
Try our free BMI calculator above to check your personal BMI instantly. It's important to understand that BMI has limitations — it doesn't account for muscle mass, bone density, or where fat is stored on your body. Someone very muscular may have a high BMI but low body fat. For this reason, your GP may also consider waist measurement and other health markers when assessing your weight health, rather than BMI alone.
- 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 know if I'm too heavy for my height?
Use our free BMI calculator to find your personal BMI, then compare it to NHS guidelines (18.5–24.9 is healthy for most UK adults). However, BMI is a screening tool only — it doesn't account for muscle, age, or medical conditions. Your GP can give you personalised advice about whether your weight affects your health.
What's the difference between kg, stone, and pounds?
In the UK, weight is measured in kilograms (kg) for clinical purposes, and stone/pounds (st/lbs) in everyday use. 1 stone = 14 lbs, and 1 kg = 2.20462 lbs. Our weight converter above can instantly switch between all three units.
Is being "heavy" the same as being unhealthy?
Not necessarily. Weight is just one factor in health. Some people at higher weights are metabolically healthy, while others at lower weights may have health risks. What matters is your individual health markers — blood pressure, blood sugar, fitness level, and how you feel. Talk to your GP about your personal health context.
What does the NHS recommend for healthy weight?
The NHS recommends a BMI between 18.5 and 24.9 for most adults (lower for South Asian and other ethnic groups). For specific height, a healthy weight range varies — our BMI calculator shows the healthy range for your height instantly.
Can weight loss medications help if I'm too heavy?
Prescription weight loss medications like Mounjaro and Wegovy may help adults with obesity or overweight with health conditions, but they require clinical assessment and are used alongside diet and exercise. Your GP or a licensed prescriber can assess whether medication is appropriate for you.
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.