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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Is 8.9 kg in stone a healthy weight?
8.9 kg is equivalent to 1 stone and 0.1 pounds — a very light weight that would only be healthy for very young children. For adults, whether this weight is healthy depends entirely on your height. Using our free BMI calculator above, you can instantly check whether your weight falls within the NHS healthy range for your specific height. This guide explains how to interpret your result and what the NHS recommends.
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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 for UK adults by height
Whether 8.9 kg is healthy depends on your height. The NHS uses BMI (body mass index) to assess healthy weight ranges. According to NHS guidelines, a healthy BMI falls between 18.5 and 24.9 for most adults.
The table below shows the healthy weight range in kilograms and stone for different heights:
- 160 cm (5ft 3in): 47–64 kg (7st 6lbs – 10st 1lbs)
- 165 cm (5ft 5in): 50–68 kg (7st 12lbs – 10st 10lbs)
- 170 cm (5ft 7in): 53–72 kg (8st 5lbs – 11st 5lbs)
- 175 cm (5ft 9in): 57–77 kg (8st 13lbs – 12st 1lbs)
- 180 cm (5ft 11in): 60–81 kg (9st 6lbs – 12st 10lbs)
- 185 cm (6ft 1in): 63–85 kg (9st 13lbs – 13st 5lbs)
If you need to convert your weight between kilograms and stone, use our free weight converter tool on this page for gradual improvement across all measurements.
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.
What to do if your weight is outside the healthy range
If your weight falls outside the healthy range for your height, the NHS recommends speaking to your GP for personalised guidance. They can assess your individual circumstances, including family history, fitness level, and any health conditions.
A healthy BMI is just one indicator — waist measurement also matters. Men should aim for under 94 cm (37 inches); women under 80 cm (31.5 inches). Even small changes of 5–clinically studied weight loss can bring real health benefits including improved blood pressure, better blood sugar control, and reduced joint strain. Your GP can discuss sustainable lifestyle changes tailored 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.
What does 8.9 kg equal in stone and pounds?
8.9 kg equals 1 stone and 0.1 pounds (or approximately 19.6 lbs). This is an extremely light weight for adults and would typically only be healthy for infants or very young children. For context, the average UK adult weighs 78 kg (12st 4lbs).
How do I know if my weight is healthy?
Use the BMI calculator on this page with your height and weight. A healthy BMI is 18.5–24.9 according to NHS guidelines. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower healthy range of 18.5–22.9. Your GP can provide personalised advice.
What if I'm significantly heavier or lighter than the healthy range?
If you're outside the healthy range, speak to your GP. They can discuss your individual health, medical history, and safe ways to reach a healthier weight. Never attempt extreme dieting — the NHS recommends losing no more than 0.5–1 kg per week for sustainable results.
Does BMI tell the whole story about healthy weight?
BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, bone density, or where fat is stored. Waist circumference is also important — the NHS recommends measuring your waist as part of a full health picture. Your GP can help interpret your results.
Can I use the weight converter for other measurements?
Yes. Our free weight converter tool on this page converts between kilograms, stone, and pounds instantly. It's useful for understanding NHS health guidance (which uses kg) alongside UK everyday measurements (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.