An approach is provided for synchronizing an impedance cardiography (“ICG”) measurement period with an electrocardiography (“ECG”) signal to reduce patient (105) auxiliary current. The approach involves measuring an ECG signal of a patient via an ECG device (103). The approach also involves processing the ECG signal to cause, at least in part, a detection of one or more ECG features of the signal. The approach further involves synchronizing a start, a stop, or a combination thereof of a measurement of an ICG signal of the patient via an ICG device (101) based, at least in part, on the detection of the one or more ECG features. The measurement of the ICG signal includes injecting an electrical current into the patient (105) for a duration of the measurement.