Abstract: A position determination device and system for determining and registering an injection location of a liquid drug administered on a body part of a user. The position determination device and system includes a position determination element configured to provide a position signal representing a current location of the position determination device, and one or more processing units configured to derive data representing an actual injection location based on the user in response to a current location being determined by the position determination unit. The position determination device can be further configured for determining a dosage activity performed by a liquid drug administration device based on obtaining at least one vibration signal from a vibration determination element.