Gary A. Maassen, M.D.

Gary A. Maassen, M.D.

South County Internal Medicine

5034 Griffin Road,
St. Louis, MO 63128

Phone: 314-843-7333

Fax: 314-843-9946


Internal Medicine


American Board of Internal Medicine


St. Louis University
St. Louis, MO


St. John's Mercy Medical Center
St. Louis, MO


Des Peres Hospital
Mercy Hospital South
St. Clare Hospital

Professional Notes

Dr. Maassen participated in Operation Desert Storm. He received the Air Force Achievement Medal, the United Nations Outstanding Unit Award, and a Service Medal.

Dr. Maassen has been selected by his peers for inclusion in Best Doctors in America ® from 2015 to 2020.

Dr. Maassen has been awarded Recognition by the National Committee for Quality Assurance (NCQA) and the American Diabetes Association for patient care in Diabetes. NCQA, in partnership with the American Diabetes Association, developed the Diabetes Recognition Program to recognize clinicians who have met standards demonstrating delivery of high quality care to patients with diabetes.

Personal Notes

Dr. Maassen is married to a nurse and they have two children.