Epigenetic age testing

What happens

A saliva or blood sample is analysed for DNA methylation at hundreds of thousands of sites. An algorithm — Horvath, GrimAge, DunedinPACE and others — converts that pattern into an estimated biological age or a pace of ageing.

How to read the result

The useful output is the trend across repeated tests on the same platform, not the single number. Clocks trained on mortality data, such as GrimAge and DunedinPACE, correlate with outcomes more strongly than first-generation clocks.

Where it stops

Results vary between laboratories and between clocks, and a single test cannot be compared with a friend's result from another provider. No clock has been shown in a trial to change outcomes when it is used to steer treatment.