IEEE 802.15.6 facilitates communication in the vicinity of or even inside a human body to serve heterogeneous medical, consumer electronics, and entertainment applications. This standard operates in beacon and nonbeacon communication modes, and each mode employs different protocols, including CSMA/CA, for resource allocation on the channel. The CSMA/CA protocol presented in IEEE 802.15.6 allows quick and prioritized access to the channel by differentiating contention window bounds of nodes with different priorities. This paper provides a simple and accurate analytical model to estimate the throughput, energy consumption, and delay of this protocol for different priority classes, under the assumption of a finite number of nodes in saturated and lossy channel conditions. The accuracy of the proposed model is validated by simulations. The results obtained in this paper can be used to design standard priority parameters for medical and non-medical applications Abstract-IEEE 802.15.6 facilitates communication in the vicinity of or even inside a human body to serve heterogeneous medical, consumer electronics, and entertainment applications. This standard operates in beacon and non-beacon communication modes, and each mode employs different protocols, including CSMA/CA, for resource allocation on the channel. The CSMA/CA protocol presented in IEEE 802.15.6 allows quick and prioritized access to the channel by differentiating contention window bounds of nodes with different priorities. This paper provides a simple and accurate analytical model to estimate the throughput, energy consumption, and delay of this protocol for different priority classes, under the assumption of a finite number of nodes in saturated and lossy channel conditions. The accuracy of the proposed model is validated by simulations. The results obtained in this paper can be used to design standard priority parameters for medical and non-medical applications.