After a doctor completes medical school and is licensed to practice medicine, the physician may pursue a rigorous 3 year training program in Internal Medicine. After passing an examination and completing the requirements, the doctor is eligible to become Board Certified in Internal Medicine. An internal medicine specialist is also called an Internist. This is different from an intern, who is a doctor that has completed medical school and is in his or her first year of post-graduate medical training. Internists are sometimes primary care doctors that are experts in managing complex diseases. Internal medicine specialists are experts in diagnosis and managing the care of patients with chronic diseases and those with multiple diagnoses. Doctors who specialize in the care of hospitalized patients are known as hospitalists.