Dr. Mercola is an osteopathic physician, also known as a DO. DOs are licensed physicians who, similar to MDs, can prescribe medication and perform surgery in all 50 states. DOs and MDs have similar training requiring four years of study in the basic and clinical sciences, and the successful completion of licensing exams. But DOs bring something extra to the practice of medicine. Osteopathic physicians practice a "whole person" approach, treating the entire person rather than just symptoms. Focusing on preventive health care, DOs help patients develop attitudes and lifestyles that don't just fight illness, but help prevent it, too.