CATHETER INSERTION DEVICE (1), COMPRISING A CATHETER HUB (5) IN WHICH A CHECK VALVE (7) IS ARRANGED, AND A CATHETER (4), WHICH IS IN FLUID COMMUNICATION WITH THE CATHETER HUB (5), WHEREIN A SUPPORT ELEMENT (20) IS ATTACHED AT THE CATHETER (4), AND A FLEXIBLE BUFFER ELEMENT (40) IS PROVIDED BETWEEN SUPPORT ELEMENT (20) AND CATHETER HUB (5). FIG. 7