(SAN ANTONIO, TX – April 21, 2016) Our community is experiencing a critical shortage of O negative blood. Some surgeries at University Hospital have been postponed because O negative blood is in short supply throughout the region. If you are O negative, you are asked to donate today. You can go to the Blood Donor Room on the third floor of University Hospital, or visit the South Texas Blood and Tissue Center. For more information, call 210-358-2812.