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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8.9 Stone In Kg — Is This a Healthy Weight?
8.9 stone is equivalent to 56.5 kilograms. Whether this weight is healthy for you depends on your height, age, and individual health factors. The same weight can be perfectly healthy for one person and overweight for another. Using our free BMI calculator, you can check where your weight sits in relation to NHS healthy weight guidelines. This guide explains how to interpret your weight in kg, shows healthy weight ranges for different heights, and gives you practical next steps based on NHS recommendations.
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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.
Healthy Weight Ranges By Height
To understand if 56.5kg is healthy, you need to calculate your BMI (Body Mass Index). The NHS defines a healthy BMI as 18.5 to 24.9 for most UK adults. The same weight produces different BMI values at different heights — that's why there's no single "healthy weight" for everyone.
Here's how 56.5kg (8.9 stone) sits across common UK heights:
- At 158cm (5ft 2in): BMI of 22.6 — healthy weight range
- At 165cm (5ft 5in): BMI of 20.8 — healthy weight range
- At 173cm (5ft 8in): BMI of 18.9 — healthy weight range
- At 180cm (5ft 11in): BMI of 17.4 — underweight (below 18.5)
Use the weight converter on this page to check how kilograms convert to stone and pounds for your reference, then input your own height into our BMI calculator to get your exact result.
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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.
Beyond BMI — What Else Matters
BMI is a useful screening tool but doesn't tell the whole story. Waist circumference is equally important — it indicates where your body stores fat, which affects health risk. For men, waist over 94cm (37 inches) suggests increased risk; over 102cm (40 inches) is high risk. For women, over 80cm (31.5 inches) indicates increased risk; over 88cm (35 inches) is high risk.
The NHS also considers age, family history, activity level, and existing health conditions. If you're 56.5kg and your BMI falls in the healthy range for your height, that's positive. If it falls outside the healthy range, discuss with your GP about safe next steps — whether that's lifestyle changes, further assessment, or weight management support.
- 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 convert 8.9 stone to kilograms?
Simply multiply 8.9 by 6.35029. This equals 56.5kg. You can also use our free weight converter on this page to switch instantly between stone, pounds, and kilograms. It handles all conversions for you, including compound measurements like "10 stone 7 pounds."
Is 56.5kg a healthy weight for everyone?
No. A healthy weight depends on height, age, sex, and muscle mass. At 165cm, 56.5kg is healthy. At 180cm, it may be underweight. At 150cm, it may be overweight. Use your height with the BMI calculator on this page to find your personal result and healthy weight range.
What's the difference between kg to stone conversion and health assessment?
Converting kilogram to stone conversion simply changes units — 56.5kg stays the same whether you call it 8.9 stone or 56.5kg. Health assessment uses BMI, waist measurement, and medical history. Both matter: conversion helps you understand the number, BMI tells you if it's healthy for your height.
What should I do if my weight is outside the healthy range?
Start by measuring your waist circumference and discussing your result with your GP. They can assess your individual health context, consider weight-related conditions, and recommend appropriate support. This might include lifestyle changes, referral to weight management services, or prescription options depending on your circumstances.
Where can I find my personal healthy weight range in stone?
Calculate your BMI using the tool on this page. Your healthy weight range is between BMI 18.5 and 24.9 for your height. Convert that to stone using the weight converter. For most UK adults aged 18–65, this gives you your personal healthy weight target in stone and pounds.
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.