A method for measuring an analyte in a whole blood sample comprising the steps of (1) bringing the whole blood sample into contact with a first substance which is carried on an insoluble carrier and specifically binds to the analyte to be measured and a second substance which is labeled with an alkaline phosphatase and specifically binds to the analyte to be measured, and (2) measuring a resulting complex on the basis of an enzyme reaction of the alkaline phosphatase, the measuring step (2) being carried out in the presence of an inhibitor of endogenous alkaline phosphatases, is disclosed.