Biological Age Tests: The Complete Guide
Methylation clocks are a trend, not a lifespan certificate
Biological-age tests are a 2026 longevity trend: a spit or blood kit returns a number that is supposed to be younger or older than your birthday. The clocks were trained on different targets, so two labs can disagree. A lower score does not prove you will live longer. Repeat the same assay if you repeat it at all, and change ApoB, blood pressure, muscle, and sleep before you buy a second kit.
Frequency
Once, if at all, after the boring labs
Duration
Same assay a year later only if a decision depends on it
Level
Intermediate
Key Takeaways
- 1Two clocks can disagree because they were built for different questions
- 2A younger number is not proof of a longer life
- 3Retest only the same lab, under the same conditions
- 4ApoB, blood pressure, a DEXA, and a walk change more than the souvenir
Who this is for
- ·Anyone about to buy a biological-age test because a podcast named it
- ·Readers who already have lipids and blood pressure handled
- ·People comparing clocks as if they were the same test
What the Number Is
Moderate EvidenceMost consumer kits estimate age from DNA methylation, sometimes mixed with blood proteins or routine labs. PhenoAge-style scores use clinical bloodwork. Methylation clocks use CpG sites. They are not interchangeable.
A review of aging clocks is clear that clinical usefulness is still under study. The score is a model output, not a diagnosis.
When It Is Worth It
Moderate EvidenceBuy one only if the result would change a habit you are not already doing. If you do not lift, sleep, or know your ApoB, the kit is entertainment.
If you retest, use the same company and similar conditions. Switching brands and celebrating a five-year drop is how the number gets gamed.
Skip
Moderate EvidenceQuarterly retests. Stacking three clocks and averaging them. Treating a younger score as permission to skip blood pressure, a DEXA, or a prescribed statin. Any kit sold as proof you reversed aging.
As an Amazon Associate, Reo Tuku Iho Limited earns from qualifying purchases through Amazon links on this site. Full disclosure
Sources
Key references cited in this guide. Links open the original publication or abstract.
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