Biomarkers and Biological Age Tests: What They Can and Cannot Tell You

What this page covers

A "biological age" test claims to tell you how old your body is, as opposed to how many birthdays you have had. Companies sell these tests directly to consumers, often next to blood panels. This page is the overview of the testing area. It explains the kinds of measures, how researchers decide whether a test is any good, and where the science stops. Detailed pages follow for each test type. This is education only. It does not tell you which tests to buy or what a result means for you.

Three questions every test must answer

The FDA describes two of them: whether a test can accurately and reliably measure what it claims to measure (analytical validity), and whether the measurement is predictive of a certain state of health (clinical validity). [1] A third question matters most to a person: clinical utility, meaning whether acting on the result leads to better health. Researchers writing in Cell say the lack of standards and consensus on what makes a reliable aging biomarker still hinders development and validation for clinical use. [2]

Biomarkers of aging

A biomarker is something you can measure that stands in for a body process. Blood pressure and cholesterol are everyday examples. In aging research, "biomarkers of aging" are measures meant to predict biological age and, ideally, to change when an intervention works. [3]

In 2025 an international expert panel used a three-round voting process and reached agreement on 14 potential biomarkers of aging for use in intervention studies. They spanned blood markers such as high-sensitivity C-reactive protein, physical function measures such as grip strength and gait speed, blood pressure and DNA methylation (epigenetic) clocks. [4] Note the purpose: these are candidate outcome measures for research studies, not a personal scorecard. The panel said future work must still find which combination is most useful. [4]

Surveyed experts also named six key barriers to using aging biomarkers in clinical practice, including the need to validate markers that are robust and responsive at the level of individuals, not only groups. [3]

Label: established for ordinary clinical measures your clinician uses, such as blood pressure; promising but limited for aging-specific biomarker panels.

The test families

Biological age tests (epigenetic clocks)

Most consumer biological age tests use an epigenetic clock, a computer model that reads chemical tags on DNA and estimates an age. A 2025 review in Nature Reviews Genetics described these as machine-learning tools used to estimate age and to judge whether anti-aging interventions work, and said many computational and statistical challenges remain that limit how they can be understood and applied. [5] A 2024 review in Nature Medicine said no consensus exists on how biomarkers of aging should be validated before they are used in the clinic. [6]

Results also depend on which clock is used. In a randomized trial of two years of calorie restriction in 220 adults without obesity, one clock measuring the pace of aging (DunedinPACE) showed a slowing, but clocks such as PhenoAge and GrimAge did not change significantly, and effect sizes were small. The authors said a conclusive test would need long-term follow-up on disease and death. [7]

Label: promising but limited for research; for personal decisions, insufficient evidence that a single biological age number should guide health choices. We did not find a source showing that lowering a clock score by itself lowers a person's risk of disease or death.

Metabolic testing and home kits

"Metabolic testing" is a loose marketing term. It can mean routine blood sugar and cholesterol tests ordered by a clinician, at-home kits, or glucose sensors worn by people without diabetes. Proper evidence not found that consumer metabolic testing as a package lengthens healthy life: we searched PubMed for trials and systematic reviews and found no source we could read that tested this. See Nutrition Tracking and Continuous Glucose Monitors and Biomarker Tracking and At-Home Tests.

Questions to ask before paying for a test

• What exactly is measured, and has it been tested against real health outcomes, not just against age?
• If I repeat the test, do I get the same answer?
• What would I do differently with the result, and would my clinician agree?
• Is the result compared with people like me (age, sex, ancestry)?

For the bigger picture see healthspan and lifespan, the limits of longevity research and talking with a health professional.