Disclosed is an improved system and method for accessing blood in a flash chamber of an intravenous catheter insertion device. The improved device is mounted on the outside surface of the intravenous catheter insertion device and carries a plunger which moves within the barrel of the device to push on the flash chamber to compress the flash chamber and expel blood through a needle coupled to the flash chamber. Various sizes and/or shapes for the plunger may be provided to accommodate different instances of intravenous catheter insertion devices, and one plunger may be chosen based on a characteristic of the insertion device (e.g., for example, the size or shape of the barrel). This device accommodates other variables in such intravenous catheter insertion devices, such as different kinds of flash plugs (removable/non-removable). The different sizes and/or shapes of the collar may include a collar which has two different configurations, one at either end, and the plunger may be reversed to change the configuration to adapt it to a different intravenous catheter.
