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
Is 8.9 Kilos a Healthy Weight?
8.9 kilos (19.6 pounds) is a relatively light weight, but whether it's healthy entirely depends on your height and age. For an adult, this weight only falls within a healthy range for very short individuals. Use our free BMI calculator to check whether your weight is in the healthy range for your specific height. The NHS uses both weight and BMI to assess health, alongside other factors like waist circumference and any existing medical conditions.
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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
The NHS healthy weight range for adults is a BMI between 18.5 and 24.9. However, what counts as "healthy" at 8.9kg varies dramatically by height. At this weight, you would need to be quite short for it to fall within a healthy range. For example, at 4ft 6in (137cm), a weight of 8.9kg gives a BMI of 4.7 — far below the healthy range. At 5ft 2in (157cm), 8.9kg gives a BMI of 3.6 — also well below healthy levels.
To find your healthy weight range, use our weight converter and BMI calculator above. These tools help you convert kilograms to stone and pounds, then calculate whether your weight falls within NHS guidelines for your height. If you need guidance on healthy weight for your height, your GP can provide personalised advice based on your individual health profile.
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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.
NHS Guidance and When to Seek Advice
According to NHS guidance, a weight of 8.9kg in an adult would be considered significantly underweight (BMI below 18.5). Being underweight can carry health risks including weakened bones, reduced immune function, and nutritional deficiencies. If you or someone you know weighs around 8.9kg as an adult, speaking with your GP is important to rule out underlying health conditions and ensure adequate nutrition.
For children, weight assessment is different — paediatric growth charts are used instead of adult BMI categories. If you're concerned about a child's weight, speak with your health visitor or GP. Remember that healthy weight is just one aspect of overall health; factors like physical activity, diet quality, and mental wellbeing also matter significantly.
- 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 8.9 kilos in pounds?
8.9 kilos equals 19.6 pounds. To convert kilograms to pounds, multiply by 2.20462. You can use our free weight converter above to switch between kg, stone, and lbs instantly.
Is 8.9 kilos a healthy weight for an adult?
For most adults, 8.9kg would be significantly underweight. Healthy weight depends on your height and age. At 5ft 4in (163cm), a healthy weight range is roughly 47–63kg. Use our BMI calculator to check your personal healthy range.
How do I know if my weight is healthy?
The NHS recommends using BMI alongside waist circumference and health history. Our free BMI calculator calculates your BMI instantly using your height and weight, and shows whether you fall within the healthy, overweight, or obese range.
What should I do if I'm underweight?
If you're significantly underweight, speak with your GP. They can check for underlying health conditions, nutritional deficiencies, or eating disorders, and provide personalised guidance on reaching a healthy weight safely.
How do I convert kilos to stone and pounds?
Divide kilograms by 6.35029 to get stone. For example, 8.9kg ÷ 6.35029 = 1.4 stone (approximately 1 stone 6 pounds). Our weight converter above does this instantly.
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.