Wireless sensor networks are widely used for healthcare applications. A new field known as wireless body area networks (WBAN) has emerged to support this area. An energy efficient medium access control (MAC) protocol can increase the performance of such a network. The major requirements for a WBAN MAC protocol are energy efficiency and low delay. In this paper, we propose a MAC protocol for WBAN using wakeup radio mechanism. We present a detailed analytical model for both energy consumption and delay. We have simulated the proposed MAC and compared the results. It is found that the proposed MAC has improved the performance in terms of energy consumption and delay.