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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How to Determine Your BMR — UK Health Guide
Your basal metabolic rate (BMR) is the number of calories your body burns at rest just to maintain essential functions like breathing, circulation, and cell production. Determining your BMR helps you understand your daily calorie requirements and can support sustainable weight management decisions. Whether you're planning lifestyle changes or exploring weight loss options, knowing your BMR is a practical starting point for understanding your metabolic health.
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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 Using Standard Formulas
The two most widely used formulas for calculating BMR are the Harris-Benedict equation (1919) and the Mifflin-St Jeor formula (1990). The Mifflin-St Jeor formula is generally considered more accurate for modern populations.
Mifflin-St Jeor Formula:
- Men: (weight in kg × 10) + (height in cm × 6.25) − (age × 5) + 5
- Women: (weight in kg × 10) + (height in cm × 6.25) − (age × 5) − 161
Example: A 30-year-old woman weighing 70kg and 165cm tall would have a BMR of approximately 1,484 kcal per day. Once you know your BMR, multiply by an activity factor (1.2–1.9) to estimate total daily calorie expenditure. Our free BMI calculator and weight converter can help you verify your measurements in both metric and imperial units.
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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.
Why BMR Matters for Weight Management
Your BMR represents roughly 60–75% of your daily energy expenditure, making it fundamental to understanding weight loss and gain. A higher BMR means your body burns more calories at rest, while factors like age, muscle mass, genetics, and hormones influence your individual rate. Weight loss typically requires a calorie deficit, but knowing your BMR helps you set realistic targets—the NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Understanding your BMR also helps contextualise how metabolism changes with weight loss, making it easier to plan long-term health strategies alongside healthy lifestyle changes.
- 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 difference between BMR and TDEE?
BMR (basal metabolic rate) is calories burned at rest; TDEE (total daily energy expenditure) is your BMR multiplied by an activity factor. For example, if your BMR is 1,500 kcal and you're moderately active (factor 1.55), your TDEE is approximately 2,325 kcal per day. Knowing both helps you calculate realistic calorie deficits for weight loss.
Does BMR change with weight loss?
Yes, BMR decreases as you lose weight because your body requires fewer calories to maintain a smaller mass. This is why weight loss often plateaus—your calorie needs adjust downward. This is why sustainable weight loss involves both calorie reduction and maintaining physical activity to preserve muscle mass.
How accurate are BMR calculators?
Standard formulas like Mifflin-St Jeor are typically accurate within ±10–20% for most adults. However, they don't account for individual variations in metabolism, muscle composition, medical conditions, or medications. A healthcare professional can provide more personalised guidance if needed.
Can I increase my BMR?
Yes, primarily through building muscle mass via resistance exercise—muscle tissue burns more calories at rest than fat tissue. Adequate protein intake, consistent strength training, and maintaining physical activity all support a healthy metabolic rate. Age and genetics also play roles, so realistic expectations are important.
How does BMR relate to healthy weight?
BMR helps you understand calorie needs, but healthy weight is better assessed using BMI alongside other factors. Use our free BMI calculator to check whether your current weight falls in a healthy range for your height, then use your BMR to plan sustainable dietary and activity changes with your GP if needed.
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.