A catheter system including an insertion device and a catheter device. The insertion device includes a housing, a latch, a needle for insertion into a patient; and a spring. The catheter device includes a housing comprising a chamber, and a seal disposed in said chamber. The seal is configured to reseal when the needle is withdrawn from the seal such that blood is sealed in the chamber. The spring relaxes and thereby retracts the needle entirely into the housing of the insertion device when the latch decouples from the catheter device.