Can a blood test show how old your organs are?
Blood tests can provide an estimate of biological ageing and flag the risk of specific conditions, but they cannot yet directly measure organ age. If you want to track your biological clock, DNA methylation and blood chemistry scores are the best-studied options -- but use them as a guide, not a diagnosis.
Three types of blood tests now provide a reasonable estimate of biological ageing, but none of them directly measures the age of individual organs. They work at the population level: they say something about how you are doing on average compared with people your age.
The DunedinPoAm test measures chemical changes to DNA in white blood cells and estimates how quickly a person is ageing biologically. In the underlying study, people with a higher rate of ageing had more chronic diseases, scored worse on balance, strength and walking speed, and had a greater chance of dying early. They also looked older to trained assessors. The test was developed on one specific birth cohort and is a research instrument, not yet a clinical test for individual use.
Blood chemistry scores such as PhenoAge and similar methods calculate biological age from routine blood values. In the CALERIE study, caloric restriction measurably slowed biological ageing as captured by these scores, and in several studies they predicted healthy lifespan even slightly better than DNA methylation tests. Here too, the result reflects a population average, not a specific organ.
For organ-specific risks, protein profiles in the blood are more promising. A combination of 11 proteins predicted significantly better than existing clinical models which patients with diabetes would go on to develop chronic kidney disease. That is more concrete than a general 'biological age', but is limited to one organ and one condition.
Blood magnesium is not suitable as an ageing marker: it poorly reflects the amount of magnesium inside cells and is strongly dependent on kidney function. Researchers conclude that it is not a useful biomarker of ageing.
Four claims from three studies and one analysis; all associations are observational, and none of the tests has been causally validated as a measure of organ age in individuals.
Can an epigenetic age test really tell you how old your body is?
An epigenetic age test provides a meaningful indication of biological ageing, but is not yet a definitive verdict on your health. Use the result as a starting point for a conversation with your doctor, not as a fixed judgement.
Which blood values tell you something about how quickly you are biologically ageing?
Blood values such as protein profiles, DNA methylation patterns, telomere length and common inflammatory markers each provide an indication, in their own way, of how quickly you are biologically ageing. The specialised tests are not yet standard general practice care, but your routine blood work already contains useful clues.
Can you tell someone's biological age from their face?
Your face does emit biological signals, but it is too limited and too variable to measure your biological age accurately. Take facial ageing seriously as a possible indicator, but do not rely on it as a measure of your health.
How can I measure my biological age?
Epigenetic clocks, in particular GrimAge and PhenoAge, currently offer the best estimate of your biological age, but they are not yet ready for straightforward home use and require expert interpretation.
Are biological age tests actually accurate?
Biological age tests such as GrimAge and DunedinPACE are associated with health outcomes in scientific research, but no clinical standards yet exist to use them reliably as a personal health test.
How reliable is a saliva test for biological age?
A saliva test for biological age is not yet reliable enough for personal use: average errors of seven to nine years and algorithms that are not well calibrated for saliva make the results difficult to interpret. Hold off on drawing conclusions until larger, saliva-specific validation studies become available.