Abstract: One aspect concerns a technique for detecting analyte concentrations, such as glucose concentrations, in blood or other bodily fluids. This technique utilizes an electrochemical test strip that includes a mediator system that generates a linear faradic response at relatively low applied potential differences. An alternating current excitation signal is applied to blood in the test strip. The alternating current excitation signal includes a low frequency signal and a high frequency signal that has a higher frequency than the low frequency signal. The glucose concentration is determined by measuring a low frequency response to the low frequency signal, measuring a high frequency response to the high frequency signal, estimating the glucose concentration based on the low frequency response, and correcting the glucose concentration for one or more error-causing variables based on the high frequency response.