Family physicians in the United States may hold either an M.D. or a D.O. degree. Physicians who specialize in family medicine must successfully complete an accredited three- or four-year family medicine residency in the United States in addition to their medical degree. They are then eligible to sit for a board certification examination, which is now required by most hospitals and health plans. American Board of Family Medicine requires its diplomates to maintain certification through an ongoing process of continuing medical education, medical knowledge review, patient care oversight through chart audits, practice-based learning through quality improvement projects and retaking the board certification examination every 7 to 10 years. The American Osteopathic Board of Family Physicians requires its diplomates to maintain certification and undergo the process of recertification every 8 years.