Using pooled data from the 2011 and 2015 waves of the China Health and Retirement Longitudinal Study (CHARLS) linked with the 2014 CHARLS Life History Survey, we analyse ex ante inequality of opportunity (IOp) in blood‐based biomarkers among Chinese adults aged 60+. We apply a re‐centered influence function approach and a Shapley‐Shorrocks decomposition to partition the contributions of different sets of measured circumstances and find that these account for between 2.01 percent and 23.95 percent of total health inequality across the range of biomarkers. The decompositions show that spatial circumstances such as urban/rural and province of residence at birth are the dominant factors for most of the biomarkers. Distributional decompositions further reveal that the relative contributions of household socioeconomic status and health and nutrition in childhood increase in the right tails of the distribution, where the clinical risk is focused, for most of the biomarkers.