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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11.8 kg in Lbs — What BMI Does This Weight Give?
11.8 kg converts to approximately 26 lbs (26.0 pounds to be precise). However, your BMI at this weight depends entirely on your height. A weight of 11.8 kg is quite low for an adult — it's closer to what you'd expect for a child or infant. This guide shows what BMI this weight produces at different heights and where it falls in NHS health categories. Use our free BMI calculator above to check your personal BMI instantly using your exact weight and height.
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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.
11.8 kg BMI at Different Heights
Your BMI is calculated by dividing weight in kilograms by height in metres squared. At 11.8 kg, here's how BMI varies across typical adult heights:
- At 150 cm (4ft 11in): BMI of 5.3 — severely underweight
- At 160 cm (5ft 3in): BMI of 4.6 — severely underweight
- At 170 cm (5ft 7in): BMI of 4.1 — severely underweight
- At 180 cm (5ft 11in): BMI of 3.6 — severely underweight
These BMI values are exceptionally low and fall far below the NHS healthy weight range of 18.5–24.9. A weight of 11.8 kg is not typical for any adult. If you're calculating BMI for a child, use age and sex-specific growth charts instead — contact your GP or health visitor for guidance.
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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.
NHS BMI Categories & When to Seek Help
The NHS categorises BMI as: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), and obese (30.0+). A BMI below 18.5 indicates being underweight, which can signal malnutrition or underlying health conditions. Severely low BMI values like those at 11.8 kg require urgent medical attention. If this is your actual weight, contact your GP immediately to discuss your health and nutritional status. Your GP can assess whether there are underlying causes and recommend appropriate support. For children, always use the NHS Healthy Weight Calculator with age and sex data rather than adult BMI thresholds.
- 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 11.8 kg convert to in pounds and stone?
11.8 kg equals approximately 26 lbs (or 1 stone 12 lbs when expressed in metric to imperial weight). To convert kilograms to stone, divide by 6.35 — so 11.8 ÷ 6.35 = 1.86 stone. Convert between units easily using our free weight converter above.
Is 11.8 kg a healthy weight for an adult?
No. 11.8 kg is not a healthy weight for any adult regardless of height. It falls far below the NHS healthy weight range and indicates severe underweight status. If this is your actual weight, contact your GP urgently to discuss your health, nutrition, and any underlying medical causes.
What does BMI mean and why does height matter?
BMI (Body Mass Index) measures body weight relative to height using the formula: weight (kg) ÷ height (m)². Height matters because the same weight on a taller person gives a lower BMI than on a shorter person. BMI helps identify health risks associated with being underweight, overweight, or obese according to NHS guidelines.
Can I use adult BMI calculators for children?
No. Children's BMI uses age and sex-specific growth charts, not adult categories. If you're checking a child's weight, always consult your GP or health visitor. They can assess whether growth is appropriate using NHS growth reference charts specific to your child's age and sex.
What should I do if my BMI is severely low like at 11.8 kg?
If you're at this weight, seek medical attention from your GP immediately. Severe underweight can indicate malnutrition, eating disorders, or underlying health conditions requiring treatment and nutritional support. Your GP can assess your individual situation and recommend appropriate care pathways.
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.