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
Find Out About Your Health and Weight
If you're looking to understand your weight, health status, or weight management options in the UK, there are several key resources and tools available to help. Whether you want to calculate your BMI, convert your weight between units, or explore evidence-based weight loss approaches, understanding the basics is the first step. This guide covers what NHS guidance says about healthy weight, how to assess your current status, and what options are available if you're looking to make changes. MyWeightCheck provides free calculators and health information aligned with NHS standards to support your journey.
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.
Understanding Your Current Health Status
The best place to start is to understand where you stand right now. BMI (Body Mass Index) is a useful starting point — it's a simple calculation based on your height and weight that helps assess whether you fall within a healthy weight range according to NHS guidelines.
- Healthy BMI range: 18.5 to 24.9 (or 18.5 to 22.9 if you're of South Asian, Chinese, Black African, or Black Caribbean heritage)
- What it tells you: BMI helps identify if excess weight might increase health risks, though it doesn't account for muscle mass or where fat is stored
- Waist measurement also matters: For men, over 94cm (37in) increases risk; for women, over 80cm (31.5in) increases risk — these may be more significant than BMI alone
Use our free BMI calculator above to check your personal status instantly. You can also use our weight converter to express your weight in stone, pounds, or kilograms — whichever units you prefer for UK health contexts.
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.
Your Weight Management Options
If you're looking to manage your weight, NHS guidance recommends a sustainable approach: a healthy weight loss rate is approximately 0.5–1 kg (1–2 lbs) per week, achieved through a balanced diet and increased physical activity. The NHS also offers a tiered pathway, starting with self-help tools and community support, progressing to GP-led programmes, and specialist services for those who need additional support.
Prescription weight loss options: If you have a BMI of 30 or above (or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure), you may be eligible for prescription weight loss medication through the NHS or private prescribing. These are always prescription-only and require a clinical assessment. Our GLP-1 weight loss calculator can help you explore potential outcomes with medication, and our progress tracker lets you log your journey.
- 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's the fastest way to find out my BMI?
Use the free BMI calculator at the top of this page — simply enter your height and weight in either metric (cm/kg) or imperial (feet/inches/stone/lbs) units, and your BMI is calculated instantly. You'll also see which NHS category you fall into and what healthy weight range applies to your height.
How do I know if I'm a healthy weight for my height?
The NHS BMI categories provide guidance: a healthy BMI is 18.5–24.9 for most adults, or 18.5–22.9 if you're of South Asian or Black heritage. You can also calculate your personal healthy weight range using the BMI calculator. Remember, BMI is a screening tool — your GP can give personalised advice about your individual health.
What should I do if I want to lose weight?
Start by speaking to your GP, who can assess your health and discuss options. The NHS recommends losing 0.5–1 kg per week through a calorie deficit and increased activity. For some, prescription weight loss medication (available through NHS specialist services or private prescribing) may be appropriate — your GP or a prescriber can assess eligibility based on your BMI and health conditions.
Can I find out about weight loss injections like Mounjaro or Wegovy?
Yes. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections licensed in the UK. Clinical trials showed average weight loss of 15–21% with Mounjaro and around 15% with Wegovy, though results vary. You'll need a clinical assessment from a prescriber to determine if either is suitable for you.
Where can I find NHS guidance on healthy weight?
The NHS website has comprehensive guidance on healthy weight, weight loss, and the NHS Weight Loss Plan. Your GP can also refer you to tier 3 specialist weight management services if needed. MyWeightCheck provides free tools and NHS-aligned health information to support your understanding — use our BMI calculator, weight converter, and GLP-1 calculator to explore your options.
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.