Variants in the clusterin gene have been associated with Alzheimer's disease (AD) through replicated genome-wide studies, but the underlying mechanisms remain unknown. In this study the association of the AD clusterin common risk polymorphism rs9331888 with blood clusterin levels was tested in 104 AD subjects and 104 healthy controls. Blood clusterin levels were significantly elevated in AD patients (p < 0.05). The rs9331888 AD-risk variant was associated with low clusterin mRNA and protein levels in an allele-dose dependent manner in both groups (p < 0.001). This study indicates that the rs9331888 AD-risk variant is associated with low blood clusterin levels.