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 Is Ideal BMI According to NHS?
Ideal BMI according to NHS guidance is between 18.5 and 24.9 for most UK adults. However, what counts as ideal depends on your ethnicity, age, and individual health factors. The NHS uses BMI as a screening tool to assess weight-related health risks, though it has important limitations — it doesn't distinguish between muscle and fat, and doesn't account for where fat is stored. Understanding your ideal BMI range and what it means for your health is the first step towards making informed decisions about your wellbeing.
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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 Healthy Weight Ranges
The NHS BMI formula divides weight (kg) by height in metres squared. According to NHS guidance, here are the standard BMI categories UK adults should follow:
- Below 18.5: Underweight
- 18.5–24.9: Healthy weight (ideal range)
- 25.0–29.9: Overweight
- 30.0–34.9: Obese (Class I)
- 35.0–39.9: Obese (Class II)
- 40.0+: Severely obese (Class III)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds. A healthy BMI for these groups is 18.5–22.9, and the overweight BMI threshold starts at 23.0. This is because these populations face higher cardiovascular and metabolic disease risks at lower BMI levels. Calculate your personal BMI using our free BMI calculator above to find where you sit in these ranges.
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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.
NHS Weight Management Support and Next Steps
If your BMI falls outside the healthy range, NHS weight management services are available through your GP. The NHS provides a four-tier pathway: tier 1 offers digital tools and community support; tier 2 includes GP-led behaviour change programmes; tier 3 provides specialist multidisciplinary weight management services; and tier 4 includes bariatric surgery for severe obesity with health complications. Waiting times and availability vary by region, but your GP can refer you to local services and discuss whether weight loss support is appropriate for you. Even a 5% reduction in body weight can bring meaningful health benefits.
- 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 the ideal BMI range according to NHS guidelines?
The NHS defines ideal BMI as between 18.5 and 24.9 for most UK adults. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the ideal range is 18.5 to 22.9. Your GP can help assess what's healthy for your individual circumstances.
Why does NHS recommend different BMI ranges for different ethnicities?
Research shows these populations have higher risk of type 2 diabetes, heart disease, and stroke at lower BMI levels compared to other groups. Lower thresholds help identify health risks earlier and enable timely intervention tailored to individual risk profiles.
What are the BMI limitations I should know about?
BMI doesn't distinguish between muscle and fat — athletes may have high BMI but low body fat. It also ignores where fat is stored (waist measurement matters), and is less accurate for elderly people, pregnant women, and children who need different assessment methods.
How can I find out my ideal weight range for my height?
Use our free BMI calculator above to enter your height and current weight — it will show your BMI and the healthy weight range for your height. For personalised advice, speak with your GP who can consider your overall health picture.
What should I do if my BMI is outside the healthy range?
Start by speaking with your GP. They can assess your individual health, discuss any weight-related concerns, and refer you to NHS weight management services if appropriate. Even small steps like increasing physical activity and adjusting diet can make a real difference.
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.