We present the digital inline holographic microscopy for blood cell counting. The microscope unit contains a pinhole chip for illumination, a micro-fluidic chip, and a CMOS-chip for detection. The design is adapted and tested for blood cell diagnostics. A single hologram delivers a stack of images for all z-positions in the micro-fluidic channel and is the basic for counting of flowing cells. Images of flowing red blood cells are presented providing clinical diagnostics.