Dr. Thomas Olsen is an internal medicine specialist, providing evaluation and management of medical conditions, coordination of care, medical screenings, preventive health care, and patient education.

He is interested in promoting primary care medicine among medical students and using research as a tool in primary care.

Dr. Olsen is a professor in the Department of Internal Medicine, Division of General Internal Medicine, at Saint Louis University School of Medicine.

He is a council member of the Missouri chapter of the American College of Physicians.

Dr. Olsen has been awarded the "Best Doctor" designation by St. Louis Magazine since 2005.