How reliable is a GlycanAge test for measuring your biological age?
GlycanAge measures something real, but whether the score reliably reflects your biological age has not yet been independently proven. Treat the result as a broad indication, not as a definitive number.
The laboratory analysis behind GlycanAge is technically precise: repeated measurements of the same blood sample over 26 days consistently produced nearly identical results. Over a period of three months, the profile also remained largely stable in healthy young people. Those are good properties for a test.
There are, however, factors that can influence the outcome. In women with a menstrual cycle, glycan patterns change noticeably throughout the cycle. The timing of blood collection therefore matters, and that makes the score harder to interpret in women. Long-term trends over five to ten years are visible, but those come from follow-up of just two individuals, which is too few to base firm conclusions on.
What the test measures is linked to ageing: reduced galactosylation and sialylation and increased agalactosylation have been associated with older age and poorer health in multiple studies. Whether the score also says something causal about how quickly you personally are ageing has not yet been proven. Genetic research offers cautious indications of a causal relationship, but the researchers themselves describe that as 'suggestive'. The score is also sensitive to lifestyle changes: substantial weight loss and testosterone therapy both produced a 'younger' outcome. That is interesting, but it also means you cannot simply read the score as a fixed measure; it moves in step with your body.
A serious caveat: virtually all published studies were conducted (in part) by employees or founders of Genos Ltd and GlycanAge Ltd, the companies that sell the test. Independent confirmation by other research groups is scarce. That makes it difficult to view the findings as entirely separate from commercial interests.
This answer is based on multiple studies, some published as review articles and some as individual research papers, including one randomised study involving testosterone and metformin. Almost all studies originate (in part) from the research groups behind the commercial product, which is a serious limitation for the independence of the findings. The researchers behind the genetic causality study describe their own findings as suggestive and not proven.