embodiments of a catheter insertion device are discussed comprising : an approximately hollow cylindrical catheter sleeve , at whose distal end a catheter is attached ; a needle sleeve with a hollow needle , which is attached thereto and which , when ready for use , extends through the catheter sleeve and the catheter , and ; a needle protective element that is arranged inside the catheter sleeve while being able to move on the needle . said needle protective element has an engaging section that engages with an engaging device , which is formed in the vicinity of the needle tip , when the hollow needle is withdrawn from the catheter sleeve . a check valve is placed inside the catheter sleeve between the catheter and the needle protective element . the hollow needle , when ready for use , extends through said check valve , and the check valve automatically closes once the needle is withdrawn .