There is a test that will tell you your biological age. In fact, there are now dozens of them.
DNA methylation clocks. Proteomics panels. Transcriptomic analyses. The longevity industry has generated an extraordinary array of tools for measuring how fast you are actually ageing — not the number on your passport, but the cellular reality underneath. Millions have been spent. Protocols changed. Supplements bought. Insurance businesses launched around the results.
The problem is that many of these tests do not work the way their marketing suggests. And the science showing this has been largely ignored by an industry with a significant financial interest in your continued enthusiasm.
In 2025, researchers at Yale published findings from one of the most rigorous evaluations of biological age clocks ever conducted — testing 18 different clocks across more than 1,000 samples. What they found was not reassuring. Results fluctuated between five and ten years within a single day. The same person, tested twice, with different results measuring up to forty years apart — influenced by a single meal, a period of elevated stress, or an afternoon breathing polluted city air.
To be precise about what this means: the tests are technically consistent. Run the same blood sample twice, and you get nearly identical results. The problem is not laboratory error. The problem is that a person's biology, as measured by these clocks, is genuinely that volatile — which means that a two-year improvement in your biological age score might reflect the protocol working, or it might reflect the fact that you slept well and ate lightly before your test.
Dr Matt Kaeberlein — one of the most respected longevity researchers in the field — took four different biological age tests from the same blood sample. The results ranged across decades. His verdict was characteristically blunt: more noise than signal.
I want to be careful here about what I am and am not saying.
Epigenetics is real. The biology of ageing is one of the most genuinely important areas of science in the world right now. The underlying research on methylation patterns and their relationship to age-related disease is substantial and worth taking seriously. I am not dismissing the science — I am questioning the gap between that science and the commercial applications being built on top of it.
An industry asking people to make expensive decisions — about supplements, protocols, and interventions — based on biomarkers with this level of instability has a responsibility to be clearer about what these tests can and cannot tell you.
What should you be measuring instead? The good news is that the more reliable longevity biomarkers are also more actionable. VO2 max — your maximum oxygen uptake during exercise — predicts cardiovascular mortality more accurately than most other single measures, and it is highly responsive to training. Grip strength. Heart rate variability. Sleep architecture. Fasting glucose and insulin sensitivity. Blood panels measuring inflammation and lipid profiles.
None of these are perfect. All of them are more stable, more directly linked to outcomes, and more actionable than a methylation score that moves by a decade between breakfast and dinner.
The biological age clock field is moving fast, and the science will eventually catch up with the ambition — longitudinal data and better delivery technology will produce tools that are genuinely reliable. Some of the most serious researchers in the field are working precisely on this problem.
Until then, the honest position for anyone offering biological age testing — clinically, commercially, or as part of a wellness programme — is to use these tools for what they are genuinely good for: curiosity, engagement, and directional guidance. Not as clinical truth. Not as the basis for expensive protocol changes.
Our clients deserve that honesty. The science is excellent. Some of the products built on it are not quite as ready as their packaging suggests — and saying so is not a criticism of the field. It is a contribution to it.