The invention relates to an access device comprising: a base (1) for aligning the access device with the skin of a patient； a needle for puncturing the skin, the needle comprising a hub (2) and a cannula (10), and the needle being movably mounted in the base (1) such that it can move between a first, fully retracted, and a second, maximally extended, position； and a locking mechanism which engages when the needle retracts from the second position and reaches a discrete third position, inhibiting the needle from further retracting to the first position. According to the invention, the access device is actuatable to disengage the locking mechanism.
