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
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Check Your BMI Online With NHS Context
Checking your BMI online is quick and free — and understanding what your result means is the first step towards better health. The NHS uses specific BMI categories to help you assess whether your weight falls within a healthy range for your height. This guide explains the NHS approach to BMI, what the different categories mean, and what NHS guidance recommends if your BMI falls outside the healthy weight range. You can calculate your personal BMI using our free BMI calculator on this page, then refer to the NHS categories below to understand what your result means.
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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 What They Mean
The NHS uses a standard BMI formula to categorise weight status. BMI is calculated by dividing your weight in kilograms by your height in metres squared (kg ÷ m²). The bmi range uk guidelines are:
- Below 18.5: Underweight
- 18.5–24.9: Healthy weight (also called normal weight)
- 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)
However, the NHS also recognises that healthy bmi thresholds are lower for people of South Asian, Chinese, Black African, or Black Caribbean heritage. For these groups, a healthy bmi range is 18.5–22.9, and overweight begins at 23.0. This reflects that these populations face higher health risks from conditions like type 2 diabetes at lower BMI levels. The overweight bmi threshold in standard categories begins at 25.0, but always check with your GP if you're unsure which category applies to you.
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 Weight Management and When to Seek Support
If your BMI falls outside the healthy range, the NHS recommends speaking to your GP about your weight and health. The NHS offers a structured weight management pathway with four tiers of support: tier 1 (self-help and digital tools), tier 2 (primary care programmes), tier 3 (specialist multidisciplinary services), and tier 4 (bariatric surgery for severe cases). Your GP can assess your individual health, discuss whether prescription weight loss medication might be appropriate, and refer you to specialist services if needed. Remember that bmi limitations exist — BMI does not account for muscle mass, so athletes may have a high BMI despite low body fat. Your GP can provide personalised guidance beyond BMI alone.
- 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 BMI range is considered healthy according to the NHS?
The NHS defines healthy BMI as 18.5–24.9 for most UK adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is lower: 18.5–22.9. Your GP can advise if you're unsure which applies to you.
Can I check my BMI online accurately?
Yes. Use our free BMI calculator on this page — it uses the standard NHS formula (weight in kg ÷ height in metres squared). For most people, online calculators are as accurate as those done in a GP surgery, but your GP can provide personalised health context around your result.
What should I do if my BMI is above 25?
If your BMI falls in the overweight or obese range, the NHS recommends speaking to your GP. They can assess your overall health, discuss lifestyle changes, and if appropriate, refer you to weight management support or specialist services depending on your circumstances.
Does BMI tell the whole story about my weight and health?
No. BMI has limitations — it doesn't distinguish between muscle and fat, doesn't account for where fat is stored, and may be less accurate for elderly people or athletes. Your GP will consider BMI alongside waist measurement, blood pressure, and other health factors.
Can I access weight loss medication through the NHS?
Possibly, through the NHS specialist weight management pathway. You'll need to be referred by your GP to a tier 3 specialist service, which assesses eligibility based on BMI, health conditions, and other factors. Availability varies by region and waiting lists can be long.
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.