Making an appointment By You are encouraged to access TRICARE Online, www.tricareonline.com , 24/7 to book an appointment. TRICARE Prime beneficiaries enrolled to the Keesler Hospital may use the 1-800-700-8603 appointment line to book or cancel appointments and leave telephone consults for their primary care managers. The appointment line is open for all Keesler Hospital TRICARE Prime beneficiaries from 6 a.m.-6 p.m. Monday-Friday; they are closed on weekends and federal holidays. Active-duty personnel may begin calling at 5 a.m. Monday-Friday to meet their appointment needs. Active-duty members with acute medical problems should call the TRICARE appointment line, 1-800-700-8603, identify that you have an acute medical problem to be booked that day. If the appointment line is closed, please call the after-hours numbers1-877-794-4629. You may also access TRICARE Online, www.tricareonline.com , 24/7 to book an appointment.