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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6.3 Kilos in Pounds — Healthy Weight Guide
6.3 kilos is equivalent to 13.9 pounds. Whether this weight is healthy for you depends entirely on your height, age, and overall health. For a small child, this might be perfectly normal; for an adult, it would be significantly underweight. This guide explains how to use our free BMI calculator to assess whether your weight falls within a healthy range according to NHS guidelines, and what to do if you're concerned about your weight.
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.
Healthy Weight Ranges by Height
Your weight alone doesn't determine health — your height and body composition matter. The NHS uses BMI (Body Mass Index) to assess weight health across different heights. Here are three practical examples of how 6.3 kg (13.9 lbs) compares to healthy weight ranges:
- At 100cm tall (3ft 3in): 6.3 kg gives a BMI of 6.3, which is significantly underweight. A healthy weight range at this height is approximately 14–18 kg.
- At 150cm tall (4ft 11in): 6.3 kg gives a BMI of 2.8, which is dangerously underweight. A healthy weight range at this height is approximately 41–56 kg (9st–12st 4lbs).
- At 170cm tall (5ft 7in): 6.3 kg gives a BMI of 2.2, which is critically underweight. A healthy weight range at this height is approximately 53–72 kg (8st 5lbs–11st 4lbs).
Use our free BMI calculator above to find your personal healthy weight range based on your exact height.
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.
NHS Guidance and Next Steps
If you weigh 6.3 kg as an adult, this is well below the NHS healthy weight range and requires urgent medical attention. Contact your GP immediately if you or someone you know is significantly underweight. Underweight status can indicate serious underlying health conditions, including eating disorders, malnutrition, or metabolic problems.
Beyond BMI, the NHS also recommends checking your waist circumference and speaking to your GP about your personal health context. Weight is just one measure of health — your GP can provide tailored guidance based on your individual circumstances, medical history, and lifestyle.
- 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 6.3 kilos in pounds exactly?
6.3 kilograms equals 13.88 pounds (often rounded to 13.9 lbs). To convert kilograms to pounds, multiply by 2.20462. You can also use our free weight converter above to switch between kg, stone, and pounds instantly.
Is 6.3 kg a healthy weight for an adult?
No. For any adult, 6.3 kg is dangerously underweight, regardless of height. A healthy adult weight starts at approximately 45–50 kg depending on height. If you weigh 6.3 kg, contact your GP urgently.
How do I know my healthy weight range?
Use the NHS BMI calculator or our free BMI calculator on this page. Enter your height and current weight to see your BMI category and healthy weight range. For adults, a healthy BMI is 18.5–24.9 according to NHS guidelines.
What if I'm underweight — what should I do?
Speak to your GP. Being significantly underweight can signal eating disorders, nutritional deficiencies, or underlying health conditions. Your GP can assess your health and recommend appropriate support, which might include dietary advice, counselling, or referral to a specialist.
Does weight in pounds tell me if I'm healthy?
No. Weight alone doesn't indicate health. Your height, body composition, waist measurement, and overall fitness matter too. The NHS recommends using BMI alongside waist circumference and speaking to your GP for personalised health guidance.
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.