An intravenous catheter inserter device comprising a catheter threader body on which is slidably attached a septum activator, a catheter threader, and a needle hub. Some embodiments further include a safety bar that is configured to assist in coordinating the movement of the various components of the device during a catheterization procedure. In general, the septum activator provides a pathway through a septum of a Luer adapter. The Luer adapter comprises a wedge seal that is configured to receive a base portion of a catheter that is inserted into the Luer adapter by the catheter threader. Accordingly, the device of the present invention simultaneously accesses the vasculature of a patient while assembling the catheter into the Luer adapter. The final configuration provides an integrated unit that is attached to the patient and in fluid communication with patient's vascular system.