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 offer these tests directly to consumers, often alongside blood work and "metabolic" panels. This page explains what each kind of test measures and where the science stops. Evidence labels used here: established, promising but limited, insufficient evidence, marketing claim. This is education only, not medical advice, and it does not tell you which tests to buy.

Biomarkers

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. [1]

In 2025 a panel of international experts used a structured voting process and reached agreement on 14 potential biomarkers of aging for use in intervention studies. They included inflammation markers (such as high-sensitivity C-reactive protein), physical function measures (grip strength, gait speed, frailty index, blood pressure) and DNA methylation, or "epigenetic," clocks. [2] Note the purpose: these are candidate outcome measures for research studies, not a confirmed personal scorecard. The panel said future work must still find which combination is most useful. [2]

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

Biological age tests (epigenetic clocks)

Most consumer biological age tests use an epigenetic clock, a computer model that reads chemical tags on DNA (methylation) 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. [3]

Key limits found in the sources we read:

• Validation is unsettled. A 2024 review in Nature Medicine said no consensus exists on how biomarkers of aging should be validated before clinical use. [4]


• Clinical translation is limited. Surveyed experts identified 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. [1]


• Results depend on the clock. In a randomized trial of two years of calorie restriction (220 adults), one clock measuring the pace of aging (DunedinPACE) changed slightly, but other clocks (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. [5]

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

"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 for longevity benefit from consumer metabolic testing as a package: we searched PubMed for systematic reviews on glucose sensors and testing panels and found no source we could read that tested whether acting on such results lengthens healthy life. For glucose sensors, see Nutrition Tracking and Continuous Glucose Monitors; for home kits, see Biomarker Tracking and At-Home Tests.

How these tests are regulated (United States)

The FDA says direct-to-consumer tests for non-medical, general wellness or low-risk purposes are generally not reviewed by the FDA before they are offered, while tests for moderate to high-risk medical purposes are generally reviewed. [6] When it does review a test, it looks at whether the test measures what it claims (analytical validity) and whether the measurement predicts a state of health (clinical validity). [6] The FDA also states that as a matter of policy it generally does not review laboratory-developed tests, and it notes that direct-to-consumer tests have varying levels of evidence behind them. [6] Rules change, and this is not legal advice. We did not check other countries.

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)?

Related reading: what researchers measure as healthspan, limits of longevity research, and how to talk with a health professional.

Safety note

A test result is not a diagnosis. An unexpected result can cause worry or lead to unnecessary follow-up tests. Do not start or stop medicines or supplements because of a biological age score; discuss results with your clinician.