A detection device for detecting a blood count parameter of a blood component in a blood vessel comprising a transmitter, a receiver, a loss detector, and a processor. The transmitter injects a first transmit signal into the blood vessel at a first frequency and a second transmit signal into the blood vessel at a second frequency. The receiver receives a first receive signal at the first frequency and a second receive signal at the second frequency. The loss detector determines a first loss value on the basis of the first transmit signal and the first receive signal, and determines a second loss value on the basis of the second transmit signal and the second receive signal. The processor determines a relaxation time constant of the blood component in accordance with the frequency having the greater loss value, and determines the blood count parameter in accordance with the determined relaxation time constant.
