Radio Frequency IDentification (RFID) devices depend on the correct operation of their memory for guaranteeing accurate identification and delivery of transponder's information. In this paper, a novel approach for online testing of RFIDs based on March-BIST techniques for EEPROMs is resented. Online test is achieved by modifying the transponder's operation and access protocol to exploit the waiting time that transponders waste before being accessed. The solution was described in VHDL, simulated and synthesized to obtain area and timing results. Results show that the solution overhead is less than 0.1 %, while the timing performance allows testing up to 32-word blocks in a single waiting slot.