An object of the present invention is to provide a blood analysis method and a blood test kit, which are for performing quantitative analysis of components by precisely obtaining a dilution factor. According to the present invention, provided is a blood analysis method including a step of diluting a collected blood sample with a diluent solution; a step of determining a dilution factor by using a normal value of a normal component which is homeostatically present in blood; and a step of analyzing a concentration of a target component in the blood sample, in which the blood analysis method uses a member selected from the group consisting of a first storing instrument for storing a diluent solution, a separation instrument for separating and recovering blood plasma from the blood sample diluted with the diluent solution, a holding instrument for holding the separation instrument, a second storing instrument for storing the recovered blood plasma, and a sealing instrument for keeping the stored blood plasma within the second storing instrument, in which the diluent solution defines an amount of the normal component which is derived from the diluent solution and/or the members and may be contained in the diluent solution, and in which a volume of the blood sample is 50 μL or less, and a dilution factor of a blood plasma component in the blood sample is 14 times or more.