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 12.8 kg to Pounds a Healthy Weight for You?
12.8 kilograms equals 28.2 pounds — but whether this is a healthy weight depends entirely on your height. For a very small child or young person, this might be appropriate; for an adult, it would be significantly underweight. This guide shows how to assess whether this weight falls within a healthy range for your height using NHS guidelines, and what to do if you're concerned about your weight.
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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 12.8 kg is healthy for you, you need to know your height. The NHS uses BMI (body mass index) to assess whether a weight is healthy — this combines both weight and height into a single measurement. A healthy BMI sits between 18.5 and 24.9 for most UK adults.
Here's how 12.8 kg compares across different heights using the metric to imperial weight conversion:
- For someone 140 cm tall (4ft 7in): 12.8 kg gives a BMI of 6.5 — severely underweight
- For someone 160 cm tall (5ft 3in): 12.8 kg gives a BMI of 5.0 — severely underweight
- For someone 180 cm tall (5ft 11in): 12.8 kg gives a BMI of 3.9 — severely underweight
At 12.8 kg body weight, BMI is critically low at any adult height. Use our free BMI calculator above to check your personal BMI and see where you fall on the NHS scale.
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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.
What To Do If You're Underweight
If your weight is significantly below the healthy range, speaking to your GP is important. Unintended weight loss or being severely underweight can indicate medical issues including nutritional deficiencies, metabolic disorders, or other health conditions that need investigation.
Your GP can:
- Assess your overall health and nutrition status
- Check for any underlying medical causes
- Refer you to a dietitian if needed
- Monitor your weight over time
Use our weight converter to understand your weight in stone and pounds, and our BMI calculator to track your healthy weight range for your specific height.
- 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 12.8 kg in pounds exactly?
12.8 kilograms equals 28.2 pounds (or 28 pounds and 3.2 ounces). To convert between metric to imperial weight measurements, multiply kilograms by 2.20462. At 12.8 kg, this weight is considered severely underweight for any adult height, though it may be appropriate for young children depending on age.
How do I know if 12.8 kg is healthy for my height?
Use the NHS BMI calculator or our free BMI tool on this page. Enter your weight and height to get your BMI. A healthy BMI is between 18.5 and 24.9. At 12.8 kg, BMI will be critically low regardless of height, indicating underweight status that should be discussed with your GP.
What does severely underweight mean?
Severely underweight means BMI is significantly below 18.5 — the lower threshold for healthy weight. This can indicate nutritional deficiencies, medical conditions, or other health concerns. If you're severely underweight, contact your GP for assessment rather than attempting to lose further weight.
Should I be worried about being 12.8 kg?
At 12.8 kg body weight, yes — this is critically low for any adult and warrants a GP consultation. However, context matters: this weight may be normal for children under age 5–6 depending on individual development. If you're an adult or teenager at this weight, medical evaluation is important to identify any underlying causes.
How can I track if my weight is becoming healthier?
Use our free progress tracker on MyWeightCheck to log your weight regularly alongside your height and BMI. Track changes over weeks and months rather than daily fluctuations. Your GP can also monitor your weight at appointments and advise on safe, healthy weight gain if that's medically needed for your situation.
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.