Doximity is a social network for physicians that was started by Epocrates co-founder and former president Jeff Tangney. Doctors on the Doximity social network are encouraged to collaborate on patient treatment or identify experts for referring patients. Doximity also works well on mobile devices. The company has announced today that over 30,000 physicians are using Doximity as a platform to collaborate. About 30,000 physicians means 5% of the U.S. physician population. Doximity raised $10.8 million in series A funding this past March.