A system and method is disclosed which relates to reading test strips. The method may include reading and storing initial values of a front photodiode and a rear photodiode, reading current values of the front and rear photodiodes, detecting at least one change between initial and current values in the front or the rear photodiodes, comparing the detected value change of one of the photodiodes with the value of the other photodiode, and determining a condition of the test strip in response to the resulting comparison.