Methods for distinguishing between an aqueous non-blood sample (e.g., a control solution) and a blood sample are provided herein. In one aspect, the method includes using a test strip in which multiple current transients are measured by a meter electrically connected to an electrochemical test strip. The current transients are used to determine if a sample is a blood sample or an aqueous non-blood sample based on characteristics of the sample (e.g., amount of interferent present, reaction kinetics, and/or capacitance). The method can also include calculating a discrimination criteria based upon these characteristics. Various aspects of a system for distinguishing between a blood sample and an aqueous non-blood sample are also provided herein.