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
NICE Guidance on Obesity — Check Your Weight Status
NICE (the National Institute for Health and Care Excellence) provides clear guidance on obesity in the UK, helping adults understand their weight status and health risks. The NHS defines overweight as a BMI between 25 and 29.9, while obesity starts at BMI 30 and above. Use our free BMI calculator above to check where you fall within these ranges. Your weight category matters because it affects your risk of serious health conditions like type 2 diabetes, heart disease, and high blood pressure. Understanding your current weight status is the first step towards making informed health decisions.
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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.
NHS BMI Categories and Obesity Thresholds
The NHS defines weight categories using BMI (Body Mass Index):
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25.0–29.9 (this is where obesity uk guidance flags increased health risk)
- Obese Class I: BMI 30.0–34.9
- Obese Class II: BMI 35.0–39.9
- Severely obese: BMI 40.0 and above
NICE guidance recommends that anyone with a BMI in the overweight range or above should consider lifestyle changes. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, these thresholds are lower due to higher health risks at lower BMI levels. Am I overweight? Calculate your personal BMI using the free calculator on this page to find out instantly. Your GP can provide personalised advice based on your individual health profile and weight check results.
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.
Waist Measurement and Next Steps
BMI is useful but has limitations—it doesn't distinguish between muscle and fat. Waist measurement is equally important: for men, a waist over 94cm (37 inches) indicates increased health risk; over 102cm (40 inches) indicates high risk. For women, the thresholds are 80cm (31.5 inches) and 88cm (34.5 inches) respectively. These measurements show where fat is stored, which affects cardiovascular health more directly than BMI alone. If you're in the overweight or obese bmi uk categories, consider speaking to your GP about your healthy weight range and available support options. The NHS offers tier 1 weight management support including digital tools and community programmes. Your GP can assess whether prescription support or specialist services are appropriate for your situation.
- 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 counts as overweight according to NICE guidance?
NICE and NHS define overweight as a BMI between 25.0 and 29.9. This category indicates increased health risk compared to healthy weight (18.5–24.9). If your BMI falls in this range, lifestyle changes including diet and physical activity are recommended. Use our BMI calculator to check your personal BMI instantly.
What's the difference between overweight and obese?
Overweight is BMI 25.0–29.9, while obesity starts at BMI 30.0. Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and severe obesity (40+). Each category carries progressively higher health risks for conditions like type 2 diabetes and cardiovascular disease. Your GP can discuss what this means for your individual health.
Does NICE guidance apply to all ethnic backgrounds?
NICE acknowledges that some ethnic groups face higher health risks at lower BMI levels. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage should use lower BMI thresholds (healthy weight 18.5–22.9, overweight 23–27.4). Your GP can advise on appropriate weight targets for your ethnicity and health profile.
What should I do if I'm in the overweight or obese category?
The NHS recommends starting with tier 1 support: self-help using digital tools, dietary improvements, and increased physical activity. Your GP can refer you to community weight management programmes. If needed, they can discuss tier 2 or tier 3 specialist services, which may include prescription medication for weight loss.
Is waist measurement as important as BMI?
Yes—NICE and NHS guidance emphasise that waist measurement is complementary to BMI. It shows where fat is stored, which is particularly important for heart health. Excess abdominal fat carries higher health risk. Measuring your waist alongside calculating your BMI gives a more complete picture of your health status.
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.