The present invention relates to a method for estimating a distribution of a sample flowed from a first electrode toward a second electrode of an electrochemical test strip. A working voltage is provided between the first electrode and the second electrode for obtaining a first and a second currents, where a ratio of the first current to the second current is applied to estimate the distribution of the sample on the first and the second electrodes and an effectiveness of a measurement of a target analyte of the sample.