Abstract: The present invention relates to a sensor preparation assembly (30) for a body monitoring system, the sensor (30) comprising at least one needle, the preparation assembly comprising: a bag (26) comprising a volume of a preparation solution, the bag (26) being configured to be positioned under the sensor (30) and being configured to be pierced by the needle (32), a receptacle (28) on which the bag is arranged (26), bearing means (24) that arc movable in relation to the receptacle (28) toward a bearing position, the bearing means (24) in the bearing position being configured to cause the sensor (30) to pierce the bag (26). The invention further relates to a sensor preparation method, comprising the placement of the sensor (30) in a position that is interposed between the bearing means (24) and the bag (26), the needle (32) of the sensor (30) piercing the bag (26).