The present application discloses an apparatus for determining a health parameter of a subject. The apparatus includes one or more biometric sensors configured to detect one or more biometric signals of the subject； a memory； and at least one processor. The memory stores computer-executable instructions for controlling the at least one processor to receive the one or more biometric signals from the one or more biometric sensors； classify physiological state of the subject as one of a plurality of physiological states comprising at least a first physiological state and a second physiological state based on the one or more biometric signals, the first physiological state being different from the second physiological state； and calculate the health parameter of the subject using one of a plurality of algorithms comprising at least a first algorithm corresponding to the first physiological state and a second algorithm corresponding to the second physiological state.
