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 Your BMR and Why Does It Matter?
Your BMR (basal metabolic rate) is the number of calories your body burns at rest just to keep you alive — breathing, circulation, cell production, and body temperature regulation. Understanding your BMR is essential for weight management because it forms the foundation of your daily energy expenditure. The NHS recognises BMR as an important concept in healthy weight guidance, as it helps explain why weight loss varies between individuals and why personalised approaches work better than one-size-fits-all diets. Knowing your BMR can guide realistic calorie targets for sustainable weight loss.
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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.
How to Calculate Your BMR
BMR is calculated using your age, sex, height, and current weight. The most widely used formula in the UK is the Mifflin-St Jeor equation, which is more accurate than older methods and accounts for modern lifestyles:
- For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
For example, a 35-year-old woman weighing 70kg and 163cm tall would have a BMR of approximately 1,400 calories per day. This means her body burns around 1,400 calories daily at complete rest, without any physical activity. NHS guidance emphasises that BMR is just the starting point — your actual daily calorie burn (TDEE, total daily energy expenditure) is higher once you factor in movement and exercise. Use our free BMI calculator above to assess your weight category alongside understanding your metabolic rate.
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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.
BMR vs TDEE and Weight Management in the UK
BMR and TDEE are often confused but serve different purposes. BMR is your resting metabolic rate; TDEE is your total daily calorie expenditure including all activity. The NHS recommends a calorie deficit of approximately 500 calories per day to lose roughly 0.5kg per week sustainably. If your BMR is 1,400 calories and you're moderately active, your TDEE might be 2,100 calories — so eating 1,600 calories per day creates a 500-calorie deficit. Factors affecting BMR include age (it decreases with age), muscle mass (muscle burns more calories than fat), hormones, and genetics. For personalised weight management advice aligned with NHS guidance, your GP can discuss realistic targets based on your individual BMR, health conditions, and lifestyle.
- 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 difference between BMR and metabolism?
BMR (basal metabolic rate) is the baseline calories your body burns at rest. Metabolism is a broader term covering all chemical processes in your body, including digestion and movement. BMR is one component of your total metabolism. Understanding both helps you make informed decisions about weight management and healthy eating.
Can you increase your BMR?
Yes, you can increase your BMR by building muscle through strength training, as muscle tissue burns more calories at rest than fat tissue. Regular physical activity, adequate protein intake, and staying hydrated all support a healthy metabolic rate. However, genetics and age also play significant roles in how much your BMR can change.
Does BMR change with weight loss?
Yes, BMR decreases as you lose weight because your body has less mass to maintain. This is why weight loss often slows over time — your body burns fewer calories at a lower weight. This is why combining diet with strength exercise is recommended by the NHS to preserve muscle during weight loss.
How does BMR affect GLP-1 weight loss medication effectiveness?
Understanding your BMR helps contextualise how weight loss medications like Mounjaro or Wegovy work. These medications reduce appetite and support calorie deficit by making you feel fuller. Your BMR determines your baseline calorie needs, so a larger deficit is often easier to achieve, potentially supporting better results.
Where can I get personalised BMR and weight management advice in the UK?
Your GP is the best starting point for personalised guidance. They can assess your individual BMR, health conditions, and weight management goals. The NHS also provides free tier 1 resources including the NHS Weight Loss Plan and digital tools. For medication assessment, you may be referred to specialist tier 3 weight management services.
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.