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
Understanding Your Body's Healthy Weight Limits
Your body has natural healthy weight limits based on your height, age, and individual health factors. These limits are defined by NHS guidance on BMI, body composition, and waist circumference—not arbitrary numbers. Understanding these boundaries helps you set realistic weight management goals and recognise when your weight poses health risks. Use our free BMI calculator above to find your personal healthy weight range, which forms the foundation of evidence-based health guidance across the UK.
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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.
What Defines Your Healthy Weight Limits?
Your healthy weight limit is primarily determined by three factors: your height (which sets your BMI range), your body composition (muscle vs. fat), and your waist circumference (indicating where fat is stored). According to NHS guidance, a healthy BMI sits between 18.5 and 24.9—but this is not a rigid ceiling. For South Asian, Chinese, Black African, and Black Caribbean adults, the NHS recommends lower thresholds starting at BMI 18.5 to 22.9, as these groups face higher health risks at lower weight levels.
- Healthy weight range: BMI 18.5–24.9 for most adults
- Overweight limit: BMI 25.0–29.9 (increases health risk)
- Obesity threshold: BMI 30.0+ (significantly increases disease risk)
- Ethnicity-adjusted limits: Lower thresholds apply for certain backgrounds
Your personal limit depends on your individual health history, medications, and any existing conditions. A GP can assess whether your current weight poses specific risks for you.
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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.
Beyond BMI: Additional Health Boundaries
BMI is useful but incomplete—waist circumference and body composition matter too. The NHS emphasises that where you carry fat matters as much as how much you carry. Fat stored around your abdomen (visceral fat) poses greater cardiovascular and metabolic risk than fat stored elsewhere. Men should aim for a waist circumference below 94 cm (37 inches); women below 80 cm (31.5 inches). Use our weight converter to check your weight across different units, then track your progress with our free progress tracker to monitor both weight and waist measurements. Even modest weight loss—around 5–10% of your body weight—can meaningfully improve blood pressure, blood sugar control, and reduce disease risk.
- 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 my exact healthy weight limit?
Your healthy weight limit is a range, not a single number. Use our BMI calculator above to find your personal range based on your height. For most adults, this falls between BMI 18.5 and 24.9. However, your ideal weight within that range depends on muscle mass, frame size, and individual health factors. Your GP can provide personalised guidance for your specific circumstances.
Does everyone have the same weight limits?
No. Weight limits vary significantly by height, age, ethnicity, and health history. The NHS recommends lower BMI thresholds for South Asian, Chinese, Black African, and Black Caribbean populations due to higher disease risk at lower weights. Older adults may have different targets than younger adults. Always discuss your personal limits with your GP rather than comparing yourself to others.
What happens if I exceed my healthy weight limit?
Exceeding your healthy weight limit gradually increases risk of type 2 diabetes, heart disease, high blood pressure, certain cancers, and joint problems. Risk increases progressively—you don't face sudden danger at BMI 30, but health risks do rise meaningfully. This is why the NHS offers weight management support through specialist services and, in some cases, prescription medications like GLP-1 injections.
Can my weight limit change?
Yes. Your healthy weight limit can shift if you gain or lose muscle mass, age significantly, develop new health conditions, or experience hormonal changes. After major weight loss or gain, your metabolic needs may change. Pregnancy, menopause, and certain medications also affect healthy weight ranges. Regular GP check-ups help track whether your personal limits have shifted.
Should I aim for the lowest weight in my healthy range?
Not necessarily. The healthiest weight for you is the one you can maintain long-term through sustainable diet and activity—usually somewhere in your healthy BMI range that feels achievable. Aiming for the absolute lowest weight can be unsustainable and stressful. Focus on overall health markers (blood pressure, blood sugar, cholesterol, waist measurement) alongside weight as measures of success.
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.