A 45-year-old executive can have arteries of 60 or mitochondria of 35. The difference between your chronological age and your biological age determines how many functional years you have left, not the number on your ID. The problem: the UK and EU now have 8 different types of biological age tests available, from free apps to genetic panels costing £800. Most are smoke with fancy marketing.
In this article I break down what each test measures, what scientific evidence supports its accuracy, real costs and which are worth doing. No affiliates, no conflicts of interest. Just data.
::pull-quote{text='Biological age is not a magic number. It's a proxy for multiple systems ageing at different rates.' source='Dr Steve Horvath, creator of the epigenetic clock'} ::
TL;DR: The essentials
- Free online tests (questionnaires) have limited predictive value but are a good starting point for identifying obvious risk factors
- Standard blood tests (glucose, lipids, CRP) are affordable (£30-60) and predict mortality better than many expensive tests
- Epigenetic clocks (GrimAge, PhenoAge) are the current gold standard with solid evidence, but cost £200-400 and require blood extraction
- Telomere tests have weak evidence and high variability; I don't recommend them as a single metric
- No test measures 'THE' biological age: each one captures different aspects of ageing
What measuring biological age really means
When you pay for a biological age test, what you're buying is a mathematical prediction of your mortality and morbidity risk based on specific biomarkers. There is no single 'master clock' of ageing that everyone measures.
Recent meta-analyses in cohorts of over 10,000 people show that the best tests correlate with:
- Mortality from all causes in the next 5-10 years
- Incidence of cardiovascular disease
- Cognitive decline
- Physical frailty
But here's the crucial nuance: one test might give you 42 years and another 38 years because they measure different biological systems. Your arteries may age faster than your immune system. Your liver may be better than your kidney function.
Free tests and apps: what real value do they have?
Online calculators and questionnaires
There are dozens of apps and websites that calculate your biological age with questionnaires of 10-20 questions about diet, exercise, sleep and habits.
Evidence: validation studies show weak to moderate correlations (r=0.3-0.5) with mortality. Better than nothing, but less accurate than a basic blood test.
What they actually measure: known risk factors (smoking, BMI, sedentary lifestyle) weighted with proprietary algorithms. They don't measure anything in your body directly.
Practical value: useful as a first step to identify high-impact behaviours to change. If an app gives you 10 extra years because you smoke and don't exercise, you don't need a £400 test to know what to do.
Wearable trackers (Garmin, Oura, Whoop)
Some wearables now include biological age estimates based on heart rate variability (HRV), resting heart rate and sleep patterns.
Evidence: HRV has moderate correlation with cardiovascular health and chronic stress. Biological age estimates from these devices have very limited evidence in peer-reviewed studies.
Practical value: excellent for continuous monitoring of trends (does your HRV improve with better deep sleep?), but not as an absolute biological age figure.
Blood tests: the best starting point
Basic panel (simplified PhenoAge)
A standard blood test measures:
- Glucose, HbA1c
- Full lipid profile
- C-reactive protein (CRP)
- Albumin
- Creatinine, urea
- Full blood count
- ALT, GGT (liver function)
Evidence: the PhenoAge algorithm, developed by Morgan Levine at Yale, uses 9 routine blood biomarkers and predicts mortality with accuracy similar to more expensive epigenetic clocks. Validated across multiple cohorts.
Cost: £30-60 at private laboratories. Many insurance schemes cover it with prescription.
Practical value: the test with best cost-benefit ratio for most people. Repeat every 6-12 months to track progress.
Additional advanced biomarkers
If you want more detail, add:
- Homocysteine: cardiovascular health and methylation marker
- Vitamin D: deficiency correlates with accelerated ageing
- Fasting insulin: preclinical insulin resistance
- ApoB: better cardiovascular predictor than LDL
- IGF-1: hormonal ageing balance
Additional cost: £60-110 more.
Epigenetic clocks: the current gold standard
DNA methylation (chemical modifications that activate/deactivate genes without changing the sequence) changes with predictable patterns during ageing.
GrimAge and epigenetic PhenoAge
What they measure: analyse methylation patterns across hundreds of CpG sites in DNA extracted from blood. GrimAge also incorporates plasma protein predictors.
Evidence: multiple studies show GrimAge predicts:
- Mortality from all causes (hazard ratio ~1.1 per year of acceleration)
- Time to cardiovascular disease
- Cancer risk
- Cognitive decline
It's the single most predictive biomarker available currently.
How it works: venous blood extraction (like a normal test) sent to specialised laboratory. Results in 3-6 weeks.
Cost in the UK/EU:
- TruDiagnostic (shipping to US): £350-450
- Muhdo (UK-based): £280
- Some labs starting to offer: £300-400
Limitations:
- High price to repeat frequently
- Requires 6-12 months between tests to detect significant changes
- Result has margin of error of ±2-3 years
For whom: if you're only doing one expensive test, do it after implementing changes for 6-12 months to see results. Not as a first step.
Telomere tests: weak evidence
Telomeres are the protective 'caps' of chromosomes that shorten with each cell division.
Marketing says: short telomeres = accelerated ageing.
Science says: the relationship is more complex. Meta-analyses show:
- High variability between cells in the same individual
- Poor reproducibility between measurements weeks apart
- Weak correlation with mortality when adjusted for other factors
- Don't respond predictably to interventions
Cost: £100-200.
Recommendation: don't do this as your main metric. If you want to know your telomeres out of curiosity, fine, but don't use the result for decisions or tracking.
Other available tests: what they measure
Advanced glycation tests (AGEs)
Measure advanced glycation end products in skin using non-invasive spectroscopy.
Evidence: moderate correlation with diabetic complications and skin ageing. Limited in predicting general mortality.
Cost: £60-110 at specialised clinics.
Value: interesting if you have prediabetes or diabetes. Less useful for general population.
Advanced body composition (DEXA)
Dual-energy X-ray absorptiometry measures bone density, muscle mass and fat distribution with high precision.
Evidence: sarcopenia (muscle loss) and osteopenia predict frailty and mortality independently of other factors.
Cost: £60-90.
Value: excellent for people over 45 or if you do serious strength training and want to track real muscle mass (bioimpedance is unreliable).
VO2 max tests
Measures maximum aerobic capacity in an exercise physiology laboratory.
Evidence: VO2 max is one of the most powerful predictors of cardiovascular mortality. Each MET of improvement reduces risk ~13%.
Cost: £70-110 at sports centres with laboratory.
Value: highly recommended if you exercise regularly. Shows clear improvements in 8-12 weeks of proper training.
What testing protocol makes sense
For most people, this order is optimal:
This protocol costs ~£90-135/year and gives you actionable information without breaking the bank.
Only do expensive epigenetic tests if:
- You've already optimised basic factors (how to reduce biological age)
- You can afford £300-400 without affecting your budget
- You'll use the result to adjust advanced interventions
How to choose a quality test (and what to do with results)
When evaluating a biological age test, verify:
Evidence criteria
- Peer-reviewed publications: the algorithm must be published in scientific journals with validation in independent cohorts
- Sample size: validated in >1,000 people ideally
- Longitudinal follow-up: studies that track people for years to confirm prediction
- Transparency: the provider must explain what biomarkers it uses and how they're weighted
Red flags to ignore
- Promises to 'reverse your biological age in 30 days'
- Tests that don't specify what biomarkers they measure
- Immediate results without real laboratory analysis
- Proprietary algorithms without publications
- Automatic recommendations for expensive supplements from the same provider
What to do with your results
A single number ("you have biological age 42") is not actionable. Ask for or seek:
- Breakdown by system: cardiovascular, metabolic, inflammatory
- Individual biomarkers out of range: here's the useful information
- Trend over time: a single measurement has limited context
If your CRP is elevated but everything else is fine, focus on reducing inflammation (sleep, exercise, omega-3). If your HbA1c rises, adjust carbohydrates. The details matter more than the overall figure.
::donut-stat{percentage=68 label='of people who get tests don't change behaviour afterwards. Don't be one of them.'} ::
The Longevitalis approach: action before measurement
Here's the uncomfortable reality: you already know what to improve without expensive tests. Sleep 7-8h, move daily, manage stress, eat real food, maintain relationships. These factors explain ~70% of biological age variance.
Tests serve to:
- Initial motivation (many need to see the number to act)
- Tracking progress after implementing changes
- Detecting subclinical problems before symptoms
But 80% of the benefit comes from consistently executing the basics.
At Longevitalis we design our protocols to address fundamental ageing mechanisms without needing sophisticated tests. LongeviSleep optimises nocturnal repair (the most powerful anti-ageing process you get free). Vitalis Renew+ supports morning cellular renewal with NAD+, resveratrol and quercetin in clinical doses. LongeviSkin works collagen and elasticity from within.
All three products have formulations based on the biomarkers that best correlate with biological age (inflammation, mitochondrial function, glycation, oxidative stress). They address causes, not just symptoms.
Full information and studies at longevitalis.com/productos.
Common errors when interpreting tests
Error 1: Obsessing over a single number
I saw a patient devastated because a test gave him 8 years more. His blood work was perfect. The epigenetic test captured chronic work stress that doesn't appear in blood markers.
Solution: use multiple metrics. A high figure in one test doesn't mean disaster if other markers are good.
Error 2: Repeating tests too soon
Human biology changes slowly. You need at least 4-6 months of consistent intervention to see significant changes in most biomarkers. 12 months for epigenetic tests.
Repeating monthly is wasting money and generating anxiety from statistical noise.
Error 3: Ignoring context
A recent infection, acute stress, menstruation, or poor night's sleep can temporarily alter biomarkers. If a result seems odd, repeat in 2-4 weeks before worrying.
Error 4: Comparing yourself to others
Tests predict future risk, not compare people. Your friend having biological age 30 and you having 45 means nothing if your trend is improving and theirs is worsening.
Compare yourself over time, not to population averages.
FAQ: Real questions about biological age tests
Do I need to fast for a biological age test?
For blood tests with glucose and lipids, yes: 10-12 hours fasting. Water only. For epigenetic methylation tests, usually not, but check instructions from your specific laboratory.
Do epigenetic tests work if I have medical conditions or take medication?
Yes. Algorithms like GrimAge were validated in populations including people with diseases and medications. In fact, they're especially useful for monitoring whether your treatments are working at the biological level. Always tell the laboratory about chronic medication.
Can I get biological age tests through my insurance or NHS?
Routine blood tests yes (glucose, lipids, CRP, etc.) with GP prescription. Commercial epigenetic tests aren't currently covered. DEXA for bone density is covered with indication (>65 years, osteoporosis risk factors).
How much can results vary between different epigenetic tests?
Between tests of the same type (eg two GrimAge measurements), technical variability is ~1-2 years. Between different types (GrimAge vs PhenoAge), they can differ 5-10 years because they measure different aspects of ageing. Normal and expected. Use the same test for tracking.
My test gave me biological age LOWER than my chronological age. Does that mean I'm fine?
It means your mortality risk is lower than the average for your chronological age. Excellent. But it's not a licence to neglect yourself. Keeping biological age low requires maintaining the habits that reduced it. And genetics explains part (20-30%), so comparing yourself to others is cheating.
Do biological age tests detect cancer or specific diseases?
They're not diagnostic tests. GrimAge and others can show ageing acceleration before clinical diagnosis of chronic diseases, but they don't replace specific screening (colonoscopy, mammography, PSA, etc.). If a test comes back very abnormal, your doctor should evaluate.
Is it worth getting a test before starting a longevity protocol?
Depends on your personality. If you need the number as motivation and can afford it, yes. If you're already motivated to change habits, spend that money on a good mattress, nutritional advice or a gym. Measure after 6-12 months of changes to see the reward. That approach works better psychologically for most people.
Conclusion: measure to improve, not to obsess
You have 8 types of biological age tests available in the UK and EU. Most are useful in the right context. None are magical. None are essential.
If I could choose just one: complete blood test every 6-12 months. £45 that gives real actionable information. If you want more precision after: annual epigenetic test once you've optimised the basics.
What matters isn't knowing your biological age to the decimal. It's implementing the protocols that reduce it —and keeping them up. Sleep well (sleep hygiene), move, eat real food, manage stress. Tests just confirm what your body already knows.
The difference between being functional and healthy at 70 versus frail and medicated isn't decided in a laboratory. It's decided in your daily choices over decades.
Disclaimer: This information is for educational purposes and doesn't replace professional medical advice. Biological age tests are not clinical diagnoses. Consult your doctor before starting any protocol, especially if you take medication or have pre-existing conditions. Individual results vary and no test can guarantee absolute predictions about future health.
