A catheter instrument comprising a needle having a needle tip at the distal end thereof, a monolithic needle tip shielding device made of a plastic material, a catheter hub having a catheter extending from the distal end thereof, wherein: said catheter instrument has an assembled state, in which said needle is extending in a direction from the proximal end to the distal end of said catheter instrument coinciding with the central axis of said needle tip shielding device, said catheter hub and said catheter, and in which assembled state said needle tip is exposed and protruding past the distal end of said catheter, for enabling penetration of skin and placement of said distal end of said catheter in a body cavity; said catheter instrument has a disassembled state, in which said needle tip shielding device is protecting said needle tip from accidental contact, and in which both of said needle and said needle tip shielding device is separated from both of said catheter hub and said catheter; said needle tip shielding device is comprising a fixing arrangement with a proximal side and a distal side, which fixing arrangement is comprising at least one engaging element extending parallel with said central axis from said proximal side or said distal side, which engaging element is resilient and resiliently striving from a compressed state towards an expanded state, such that it is contacting the inner surface of said catheter hub with a force in said assembled state for providing a constant spatial relationship between said needle tip shielding device and said catheter hub in said assembled state; and said needle tip shielding device is comprising at least one resilient arm extending from the distal side of said engaging element, which resilient arm, or a part thereof, coincides with the central axis of said needle in said disassembled state. said catheter instrument has an assembled state, in which said needle is extending in a direction from the proximal end to the distal end of said catheter instrument coinciding with the central axis of said needle tip shielding device, said catheter hub and said catheter, and in which assembled state said needle tip is exposed and protruding past the distal end of said catheter, for enabling penetration of skin and placement of said distal end of said catheter in a body cavity; said catheter instrument has a disassembled state, in which said needle tip shielding device is protecting said needle tip from accidental contact, and in which both of said needle and said needle tip shielding device is separated from both of said catheter hub and said catheter; said needle tip shielding device is comprising a fixing arrangement with a proximal side and a distal side, which fixing arrangement is comprising at least one engaging element extending parallel with said central axis from said proximal side or said distal side, which engaging element is resilient and resiliently striving from a compressed state towards an expanded state, such that it is contacting the inner surface of said catheter hub with a force in said assembled state for providing a constant spatial relationship between said needle tip shielding device and said catheter hub in said assembled state; and said needle tip shielding device is comprising at least one resilient arm extending from the distal side of said engaging element, which resilient arm, or a part thereof, coincides with the central axis of said needle in said disassembled state.