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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What Is My BMR? UK Guide to Basal Metabolic Rate
Your BMR (basal metabolic rate) is the number of calories your body burns at rest, just to maintain basic functions like breathing, circulation, and cell production. It's different from your TDEE (total daily energy expenditure), which includes activity. Understanding your BMR is useful for weight management because it shows your minimum calorie needs. You can calculate your BMR using formulas based on your age, weight, height, and sex, or use our free BMI calculator and weight converter to assess your overall health context alongside your metabolic needs.
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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
The most common BMR formulas are the Harris-Benedict equation and the Mifflin-St Jeor equation. The Mifflin-St Jeor is considered more accurate for modern populations.
Mifflin-St Jeor BMR formula:
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
For example, a 40-year-old woman weighing 70 kg and 163 cm tall would have a BMR of approximately 1,400 kcal per day. This is what her body burns doing nothing. Your TDEE is then calculated by multiplying your BMR by your activity level (typically 1.2 to 1.9, depending on how active you are).
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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 Loss and Health
Knowing your BMR helps you understand how many calories you need to maintain your current weight. For weight loss, the NHS recommends creating a calorie deficit of around 500 kcal per day to lose approximately 0.5 kg per week safely. Your BMR is your starting point—never aim to eat below your BMR long-term, as this can harm metabolism and muscle mass. BMR naturally decreases with age (about 2–8% per decade after 30) and with significant weight loss, so recalculating periodically is important. If you're considering weight management interventions—whether lifestyle changes or prescription options—understanding your calorie baseline helps your GP or prescriber assess the right approach for you alongside a healthy weight UK context.
- 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 is calories burned at complete rest; TDEE is total daily energy expenditure including all activity. TDEE = BMR × activity factor (1.2–1.9). For weight loss, you create a deficit from your TDEE, not your BMR. Never eat below your BMR consistently.
Does BMR change with weight loss?
Yes. As you lose weight, your BMR decreases because there's less body mass to maintain. This is called adaptive thermogenesis. Recalculate your BMR every 5–10 kg of weight loss to adjust your calorie targets. Strength training helps preserve muscle and BMR during weight loss.
Why is my BMR lower than I expected?
BMR decreases with age, slower metabolism, low muscle mass, and certain medical conditions (hypothyroidism, for example). Women typically have lower BMR than men. If your BMR seems very low, consult your GP—some conditions affect metabolism.
Can I increase my BMR?
Yes, through resistance training and building muscle mass. Muscle tissue burns more calories at rest than fat. Adequate protein intake, quality sleep, and consistent exercise also support healthy metabolism. Crash diets actually lower BMR—gradual weight loss is better.
How does BMR relate to healthy weight UK guidelines?
BMR helps personalise calorie needs, but healthy weight is determined by BMI (18.5–24.9 for most adults, or 18.5–22.9 for South Asian, Chinese, Black African, or Caribbean backgrounds). Use our free BMI calculator alongside BMR understanding for complete health context.
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.