The hand-held device detects the distance between a muscle and an outer skin layer in a body by impacting the outer surface of the skin and detecting the distance to the muscle from that point of engagement. The device includes a first end including a force sensor configured to detect the force of an impact of the first end to an associated body part. The device further includes a distance sensor provided at the first end configured to detect the distance between a skin outer layer and a muscle and a main body configured to receive a hand. The detection device includes a controller and processor to detect the impact force and distance between the skin outer layer and muscle at engagement. The device may be used in a method of determine muscle depth and/or location in connection with the prescription and/or administration of anaphylaxis medications by auto injector.
