Measuring Your True Age
Biological age testing has transformed from research curiosity into mainstream longevity tool, with epigenetic clocks now able to predict mortality risk more accurately than chronological age alone. A December 2025 study in Nature Communications comparing 14 epigenetic clocks across 18,859 individuals confirmed that second and third-generation clocks significantly outperform earlier versions in predicting disease outcomes. Understanding these tests enables tracking whether longevity interventions actually work.
The Buck Institute released a new “IC Clock” in June 2025 that measures intrinsic capacity across six key functions—mobility, cognition, mental health, vision, hearing, and nutrition—outperforming all previous clocks in predicting overall mortality. The field advances rapidly, with testing now accessible through consumer services starting around $300.
Understanding Biological vs. Chronological Age
The Fundamental Distinction
Chronological age measures time since birth—a fixed number advancing one year annually. Biological age measures functional state—how well your cells, tissues, and organs perform relative to population averages. Two people sharing a birthday can have biological ages differing by decades based on genetics, lifestyle, and cumulative health choices.
Bryan Johnson, chronologically 48, claims biological age measurements showing certain organs functioning at levels typical of much younger individuals. Whether these measurements predict actual longevity outcomes remains an active research question, but the consistency of his biomarker improvements suggests meaningful biological change.
Why Biological Age Matters
Biological age better predicts health outcomes than chronological age. Research consistently shows that individuals with biological ages younger than their chronological age experience lower disease risk and mortality, while those biologically older face elevated risks. This predictive power makes biological age valuable for both individual health decisions and intervention research.
For longevity interventions, biological age provides feedback impossible to obtain otherwise. Waiting 30 years to see if an intervention extends lifespan isn’t practical. Biological age changes measurable over months or years offer surrogate endpoints indicating whether protocols work.
Types of Biological Age Tests
Epigenetic Clocks (DNA Methylation)
The gold standard for biological age assessment, epigenetic clocks measure predictable changes in DNA methylation patterns that accumulate with age. Methylation is a chemical modification affecting gene expression without altering DNA sequence itself. These patterns shift so consistently that mathematical models can estimate age from methylation data alone.
First-Generation Clocks (Horvath, Hannum): Developed around 2013, these pioneering clocks estimate chronological age from methylation patterns. Horvath’s clock analyzes 353 methylation sites across multiple tissue types. Hannum’s clock focuses on 71 sites in blood samples. While groundbreaking, these clocks have limited predictive power for health outcomes.
Second-Generation Clocks (PhenoAge, GrimAge): These clocks train on health outcomes rather than just age, making them better predictors of disease and mortality. GrimAge, developed in 2019, combines methylation data with smoking history and plasma protein markers to predict lifespan and healthspan with remarkable precision.
Third-Generation Clocks (DunedinPACE, IC Clock): The latest generation measures pace of aging rather than just biological age—how quickly you’re aging right now. DunedinPACE provides a speedometer rather than odometer reading. The 2025 IC Clock incorporates functional capacity measures, representing the current cutting edge.
Telomere Length Testing
Telomeres—protective caps on chromosome ends—shorten with cell division and age. Shortened telomeres associate with aging and disease. However, telomere testing shows more variability and less predictive power than epigenetic clocks. A 2025 study in Genome Medicine found epigenetic clocks consistently outperformed telomere measurements for age and mortality prediction.
Telomere tests cost $100-300 and provide a single data point rather than comprehensive assessment. They may be useful alongside other measures but shouldn’t serve as primary biological age indicators.
Composite Biomarker Panels
Some services calculate biological age from combinations of traditional biomarkers: blood pressure, cholesterol, glucose, inflammatory markers, kidney and liver function. These panels provide useful health information but lack the precision of epigenetic testing. They’re often included in comprehensive health assessments alongside other measures.
Available Testing Services
Consumer-Accessible Options
TruAge (TruDiagnostic): Comprehensive epigenetic testing including multiple clock algorithms. Prices start around $500-600 for complete panels. Provides DunedinPACE (pace of aging), biological age estimates, and detailed methylation analysis.
Elysium Index: Consumer test based on epigenetic analysis, approximately $300-500. Provides biological age estimate and comparison to population averages.
EpiAge: Newer test announced in January 2025 using simplified methodology focused on three DNA sites in the ELOVL2 gene. Works with both blood and saliva samples, making testing more accessible. Researchers validated accuracy against established clocks across 4,600+ individuals including those with Alzheimer’s and HIV.
Clinical Testing
Longevity clinics like Human Longevity Inc., Fountain Life, and academic medical centers offer comprehensive biological age assessments as part of executive health evaluations. These typically include epigenetic testing alongside extensive imaging, genetic analysis, and biomarker panels. Costs range from $3,000-15,000 depending on comprehensiveness.
Interpreting Your Results
What the Numbers Mean
Biological age results typically express estimated age in years, allowing comparison to chronological age. A 45-year-old with biological age of 40 shows favorable aging; the same individual with biological age of 52 shows accelerated aging requiring intervention.
Pace of aging metrics (like DunedinPACE) express aging speed relative to baseline. A score of 1.0 indicates aging at average pace; below 1.0 indicates slower aging; above 1.0 indicates faster aging. These metrics may be more sensitive to intervention effects than point-in-time biological age estimates.
Factors Affecting Results
Multiple variables influence biological age measurements. Acute illness or stress can temporarily elevate biological age. Recent travel, poor sleep, or intense exercise may affect results. Testing during stable health periods provides more representative baselines.
Research shows biological age can fluctuate in response to stressors and recover afterward. A 2023 study found biological age increased during major surgery and pregnancy but returned toward baseline following recovery. This fluidity suggests biological age responds to interventions but also to temporary perturbations.
Using Results to Guide Interventions
Baseline testing establishes starting point for tracking progress. Repeat testing every 6-12 months measures intervention effectiveness. Look for trends rather than single readings—natural variation means individual tests carry uncertainty.
If biological age exceeds chronological age, prioritize foundational interventions: sleep optimization, exercise implementation, nutritional improvement, stress management. The CALERIE trial demonstrated that caloric restriction reduced pace of aging measured by DunedinPACE. Other research links various interventions to biological age changes, providing evidence for protocol design.
Limitations and Controversies
What Tests Don’t Tell You
Biological age tests estimate statistical risk, not destiny. An individual with favorable biological age can still develop disease; someone with unfavorable results may live healthily for decades. These tools inform probabilities, not certainties.
A December 2025 paper in npj Aging questioned whether aging clocks provide actionable advantages over simpler risk scores and direct outcome predictors. The authors argue clocks often face inconsistent clinical validation and ignored prediction uncertainty. These legitimate scientific debates remind us that biological age testing, while valuable, remains an evolving field.
Ethical Considerations
The American Medical Association’s Journal of Ethics published December 2025 analysis of epigenetic testing ethics. Concerns include patient misunderstanding of results, psychological harm from unfavorable findings, and potential age-related discrimination if biological age data influences employment or insurance. Transparency about test limitations remains essential.
Getting Started with Biological Age Testing
Pre-Testing Preparation
Test during periods of stable health—avoid testing while sick, extremely stressed, or recovering from major events. Follow provider instructions regarding fasting or timing requirements. Document current lifestyle factors (sleep quality, exercise, diet, supplements) to contextualize results.
Post-Testing Action
Review results with qualified professionals who can interpret findings in context. Develop intervention priorities based on results and broader health assessment. Schedule follow-up testing in 6-12 months to measure progress.
Whether results show favorable or unfavorable biological age, the response remains similar: optimize foundational behaviors, address identified risk factors, and track progress over time. Biological age testing provides valuable feedback on the effectiveness of longevity protocols, enabling data-driven optimization.