The invention relates to a needle assembly (1, 101, 201, 301, 401, 501, 601), comprising a hollow needle (3, 103, 203, 303, 403, 503, 603) with a flow channel (3.1, 103.1, 203.1, 303.1, 403.1, 503.1, 603.1) and a needle hub (2, 102, 202, 302, 402, 502, 602). At least one pressure sensitive element (4, 104, 204, 304, 404, 504, 604) is adapted to detect an occlusion in the flow channel (3.1, 103.1, 203.1, 303.1, 403.1, 503.1, 603.1), wherein the pressure sensitive element (4, 104, 204, 304, 404, 504, 604) is modifiable if a pressure in the flow channel (3.1, 103.1, 203.1, 303.1, 403.1, 503.1, 603.1) exceeds a predetermined value.
