The advancements in large scale integrated technology and communication technologies have resulted in the development of low cost and small size wireless sensors. They can be even injected into human body for health care. This development has put enormous impact on medical healthcare scenario. It became easily possible to replace the traditional equipments and procedures with small sized sensors. Wireless Sensor Networks is very much useful in various ‘Medicare’ applications. The involvement of Wireless Sensors provides all-time monitoring to the user and either avoids the dangerous situation or is capable to take appropriate actions in case of emergency. This paper provides an overview of the challenges in the design of wireless sensor networks for medical applications. The major design challenges such as delay, security, privacy, accuracy and reliability of data, in these applications are explored with appropriate solutions.