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 12.1 Kg (26.7 Lbs) A Healthy Weight?
12.1 kg converts to 26.7 pounds, but whether this is a healthy weight for you depends entirely on your height. A small child might be at a healthy weight at 12.1 kg, while an adult would be significantly underweight. The NHS uses BMI — a calculation based on both weight and height — to assess whether an adult's weight falls into a healthy range. Use our free BMI calculator above to find out if your weight is healthy for your specific height, or use the weight converter to switch between metric and imperial measurements.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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
At 12.1 kg, an adult would be severely underweight (BMI under 18.5), but this weight is only relevant for very young children or infants. To show how height dramatically changes what counts as "healthy", here are three real examples:
- At 163 cm (5ft 4in): A healthy weight range is 49–65 kg (108–143 lbs). At 12.1 kg, this person would be dangerously underweight.
- At 173 cm (5ft 8in): A healthy weight range is 55–75 kg (121–165 lbs). Again, 12.1 kg is far too low.
- At 155 cm (5ft 1in): A healthy weight range is 44–61 kg (97–134 lbs). 12.1 kg remains critically underweight.
The NHS defines a healthy BMI as 18.5 to 24.9 for most adults. To convert kilograms to stone or calculate your BMI across different weights, use the free tools on this page.
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.
NHS Guidance & What To Do If You're Outside The Healthy Range
If you're significantly underweight (BMI below 18.5), it's important to speak with your GP. Underweight status can indicate nutritional deficiencies, metabolic issues, or underlying health conditions. The NHS recommends discussing any significant weight concerns with your healthcare provider.
Additionally, waist measurement matters — even for underweight individuals, where fat is stored affects health. If you're concerned about your weight in either direction, your GP can refer you to appropriate support services. There's no judgment in seeking help; weight health is about overall wellbeing, not appearance. Track your weight journey using our free progress tracker to identify trends over time.
- 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 12.1 kg in pounds exactly?
12.1 kg equals 26.67 pounds (often rounded to 26.7 lbs). To convert kilograms to pounds, multiply by 2.20462. You can also use our free weight converter tool to switch between kg, stone, and lbs instantly.
Is 12.1 kg a healthy weight for an adult?
No, 12.1 kg is dangerously underweight for any adult regardless of height. Adults with this weight would have a BMI well below 18.5 (the minimum healthy threshold). This weight is only appropriate for infants or very young children.
How do I know if my actual weight is healthy?
Use our free BMI calculator above — it calculates your BMI based on your weight and height to show you whether you fall into the healthy range (18.5–24.9), overweight, or obese category. The NHS uses BMI as the primary screening tool for adults.
What should I do if I'm significantly underweight?
Contact your GP to discuss your weight and any related health concerns. Underweight status can indicate nutritional deficiencies or underlying conditions. Your GP can arrange appropriate support or referrals if needed. Never attempt rapid weight gain without medical guidance.
How can I convert between kg, stone, and lbs easily?
Our free weight converter on this page lets you instantly switch between all three measurement systems. Simply enter your weight in any unit and the converter displays the equivalent in kg, stone, and pounds — useful for comparing your weight across different standards.
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.