Different aspects of Wireless sensor networks ( WSN) are currently being studied. Some of the important aspects would be clustering, routing and security. This paper looks at the problems arising due to wireless routing between nodes of a medical WSN. Here, the focus is on selective forwarding ( SF) attacks. As a solution, we have described a secure routing protocol with test-bed simulation results. This protocol is capable of detecting and correcting the SF attack. The results show that the power consumed during the detection phase is only 152 mu W more than the power consumed during normal phase.