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
What Does 21 Stone Mean for Your Health in the UK?
21 stone is equivalent to 133.3 kilograms, which places most adults in the obese category according to NHS guidelines. Understanding what this weight means for your health, how it converts to other measurements, and what NHS guidance recommends are important first steps toward making informed health decisions. Whether you're monitoring your own weight or supporting someone else, this UK health guide provides evidence-based information to help you understand the health context of this weight.
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.
21 Stone in kg and BMI Context — NHS Guidance
21 stone converts to 133.3 kg, or approximately 293.7 lbs. To understand what this weight means for health, the NHS uses BMI (body mass index) as a screening tool. BMI is calculated by dividing weight in kilograms by height squared in metres. For an adult of average UK height (around 1.7m), a weight of 21 stone would result in a BMI of approximately 46, which falls into the severely obese category according to NHS guidelines. However, BMI varies significantly by height — use our free BMI calculator above to calculate your personal BMI instantly. The NHS notes that BMI has limitations: it doesn't distinguish between muscle and fat, nor does it account for where fat is stored, so BMI should always be considered alongside other health measures like waist circumference and overall fitness.
- 21 stone = 133.3 kg (exact conversion)
- Average BMI at this weight: approximately 46 (severely obese category)
- Waist measurement is also important — health risk increases above 94cm (men) or 80cm (women)
- For people of South Asian or Black African heritage, weight-related health risks are higher at lower BMI levels
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.
UK Health Support and Weight Management Resources
The NHS offers structured support for people managing weight at this level. If you're concerned about your health at 21 stone, speaking with your GP is the first step — they can assess your individual health picture and refer you to specialist tier 3 weight management services if appropriate. These services provide multidisciplinary support including dietitians, psychologists, and exercise specialists. Depending on your circumstances and health conditions, your GP may also discuss prescription weight management options. You can track your progress using our free progress tracker, which helps you log weight changes over time and identify patterns. The NHS recommends a sustainable weight loss rate of 0.5–1 kg per week, which means realistic and gradual progress.
- 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 21 stone in kilograms?
21 stone equals 133.3 kilograms exactly. The conversion uses the formula: stone × 6.35029 = kg. You can verify this instantly using the weight converter tool on this page, which also converts to pounds (293.7 lbs). Having your weight in kg is useful for calculating BMI and accessing NHS health guidance.
What BMI would 21 stone give me?
Your BMI depends on your height. At 21 stone, an average-height UK adult (around 1.7m) would have a BMI of roughly 46, which is in the severely obese category. Use our free BMI calculator above to enter your exact height and get your personal BMI. BMI is a screening tool but has limitations — it doesn't account for muscle mass or fat distribution.
Is 21 stone considered unhealthy?
According to NHS guidelines, 21 stone (133.3kg) would likely be associated with increased health risks for most adults, particularly regarding type 2 diabetes, cardiovascular disease, and joint stress. However, health is individual and depends on many factors including fitness level, health conditions, and ethnicity. Your GP can assess your personal health context and discuss management options if appropriate.
What weight loss support is available on the NHS?
The NHS offers tier 3 specialist weight management services, which you access through GP referral. These services provide dietitian support, behaviour change programmes, and sometimes prescription weight management medication. Availability and waiting times vary by region. Your GP can explain what's available in your area and whether you're eligible for referral.
What is a healthy weight loss rate?
The NHS recommends losing weight at 0.5–1 kg (1–2 lbs) per week for sustainable results. Faster weight loss is possible with specialist support, but rapid loss increases the risk of muscle loss. Our free progress tracker helps you monitor your weight loss pace and stay motivated over time.
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.