Epigenetic age kits report a number derived from DNA methylation at a few hundred CpG sites. Here is how that number is computed, how much of it is noise, and what to measure instead if you want something you can track.
A decade-by-decade view of which blood measurements carry information, how often to repeat them, and why interpretation gets harder after 70. Written for people who want to keep their own longitudinal record.
A technical read on epigenetic clocks, blood-chemistry clocks, and survey-based 'bio age' calculators: what each one measures, how precise it is, and how to compute one yourself from your own data.
A practical protocol for estimating functional age from physical performance tests, blood chemistry algorithms, and DNA methylation clocks, with the reliability problems that make most single-timepoint results uninterpretable.