A method for monitoring a blood glucose level in a person involves transmitting millimeter range radio waves over a three-dimensional (3D) space below the skin surface of a person. receiving radio waves on multiple receive antennas, the received radio waves including a reflected portion of the transmitted radio waves, isolating a signal from a particular location in the 3D space in response to receiving the radio waves on the multiple receive antennas, and outputting a signal that corresponds to a blood glucose level in the person in response to the isolated signal.
