Abstract: A portable, modular blood analyzer capable of analyzing multiple blood values in an inexpensive, relatively simple, easy-to-use and easy-to-maintain instrument. The invention comprises a three-part system including an analyzer body, calibrant cartridge, and sensor cartridge. A modular calibrant cartridge is insertable into the analyzer body, and contains all necessary calibrant fluids as well as a waste container. A modular sensor cartridge having integral pump tubing plugs into the analyzer body for easy removal and replacement of the sensor elements. The analyzer body internally has modular units including an electronics module, a display module, and a fluidics/printer module. The analyzer uses a single pump head to aspirate blood only to a sensor array within the sensor cartridge.