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
How Do You Test Metabolism
Testing your metabolism involves several approaches, from simple at-home calculations to clinical measurements performed by your GP or a specialist. Your metabolic rate — the number of calories your body burns at rest — influences how quickly you lose weight, how your body responds to exercise, and your overall energy levels. Understanding your metabolism is particularly useful if you're considering weight management options or trying to understand why weight loss feels easier or harder for you personally. We'll explain the main testing methods available in the UK and how they work.
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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.
Common Metabolism Tests in the UK
Basal Metabolic Rate (BMR) calculation is the simplest method and requires no clinical visit. Your GP can estimate your BMR using formulas like the Harris-Benedict or Mifflin-St Jeor equation, which account for your age, sex, height, and weight. You can also calculate this yourself using our free BMI calculator and weight converter above, which help establish your baseline health metrics.
Indirect calorimetry is a clinical test measuring oxygen consumption and carbon dioxide production to determine how many calories you burn. This is more accurate than estimates and is sometimes available through NHS weight management services or private health clinics. DEXA scans measure body composition (muscle versus fat), which affects metabolic rate — more muscle tissue burns more calories at rest. Some private health clinics offer metabolic testing packages, though NHS availability varies by region and referral pathway.
Clinically BackedWeight Loss
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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 Metabolism Matters for Weight Management
Your metabolic rate is one factor among many that affects weight loss success. If you're exploring prescription weight loss medication like Mounjaro or Wegovy, understanding your baseline metabolism helps you set realistic expectations — clinical trials show these medications support an average weight loss of 15–21% body weight when combined with dietary changes and physical activity, though individual results vary based on your metabolism, lifestyle, and adherence.
Slower metabolism may mean weight loss requires more consistent effort, but it's not a barrier to success. Your GP can refer you to NHS tier 3 weight management services, where specialists assess your full health picture — including metabolic factors — to recommend the most appropriate support. You can also track your progress using our free progress tracker alongside any weight management plan.
---COL_J_TOOLS--- Reference the BMI calculator, weight converter, GLP-1 weight loss calculator, and progress tracker naturally in the content where relevant to the topic.- 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.
Can you test your metabolism at home?
Basic BMR calculations can be done at home using online formulas or our free BMI calculator, which provides your health baseline. However, clinical tests like indirect calorimetry or DEXA scans require professional equipment and are available through private clinics or NHS specialist services. Your GP can advise which approach is most useful for your situation.
Does metabolism affect how much weight you lose with Wegovy?
Yes, metabolism is one factor influencing weight loss results. Wegovy (semaglutide) is a GLP-1 medication that works by reducing appetite and supporting feeling fuller after smaller meals. Clinical trials showed average weight loss of around 15% body weight, but individual results vary based on metabolism, diet, physical activity, and how your body responds to the medication.
What's the difference between BMR and TDEE?
BMR (basal metabolic rate) is the number of calories your body burns at complete rest, while TDEE (total daily energy expenditure) includes BMR plus calories burned through physical activity and digestion. Both are useful for understanding your calorie needs. Your GP or a dietitian can help you calculate these for personalised weight management guidance.
How do NHS weight management services assess metabolism?
NHS tier 3 specialist weight management services assess your overall health picture, including medical history, current activity level, and lifestyle factors that affect metabolism. They may recommend indirect calorimetry or body composition testing if clinically relevant. Referral is through your GP, and assessment informs whether prescription medication, behaviour support, or other interventions are appropriate.
Does having a slow metabolism mean you can't lose weight?
No. While a slower metabolism means weight loss may require a larger calorie deficit or take more time, it's absolutely possible to lose weight successfully. Weight loss depends on overall calorie balance, consistency, and individual factors. Prescription medications, structured diet programmes, and physical activity all support weight loss regardless of metabolic rate. Your GP can provide personalised guidance.
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.