a physiological characteristic sensor that includes a housing having a first housing portion coupled to a second housing portion, an antenna, and a sensor, the second housing portion having a bottom region and a sidewall extending upwardly from the bottom region, wherein the first housing portion and the second housing portion cooperate to enclose the antenna and a portion of the sensor, the antenna is coupled to the first housing portion to face a first surface of the second housing portion, and the portion of the sensor is coupled to the first surface; and

a sensor inserter configured to be coupled to the physiological characteristic sensor, the sensor inserter including a sensor retainer that is configured to couple to the sidewall of the second housing portion in a second state while the second housing portion is at least partially inside the sensor inserter and configured to be uncoupled from the second housing portion in a first state while the second housing portion is at least partially inside the sensor inserter, the sensor retainer including a central bore configured to receive the housing of the physiological characteristic sensor and a plurality of retainer arms spaced apart about a perimeter of the central bore to surround the housing of the physiological characteristic sensor, each retainer arm of the plurality of retainer arms is movable between the first state and the second state, in the first state, a terminal end of each retainer arm of the plurality of retainer arms is spaced apart from a surface of the sensor retainer to define a gap, and in the second state, the terminal end of each retainer arm of the plurality of retainer arms contacts the surface of the sensor retainer.