The present invention extends to a disinfection cap for disinfecting a male luer end of an infusion therapy device. The disinfection cap can include an internal reservoir containing an antimicrobial or saline solution which is sealed with a flexible septum to prevent the solution from evaporating. The septum can include one or more slits or pierceable seams that allow a male luer end of an infusion therapy device to be inserted through the septum and into the solution. While the male luer is inserted through the septum, the solution contacts both the inner and outer surfaces of the male luer. Because the septum reduces evaporation of the solution and prevents the solution from leaking out of the cap, the solution remains in contact with the male luer for a longer duration then when typical disinfection caps are used thereby increasing the effectiveness of the disinfectant.