Dr. Dillmann obtained his MD from the University of Munich in 1970 and completed his internship at Mt. Sinai Hospital in New York in 1971. At Montefiore, New York, Dr. Dillmann completed his medical residency in 1972 and his endocrinology fellowship in 1975. He accepted a position as Assistant Professor of Medicine, Albert Einstein College of Medicine, New York and moved to the University of Minnesota, Minneapolis, from 1976-1978.
Dr. Dillmann joined the UC San Diego faculty in 1979, becoming associate professor of medicine in 1981 and professor of medicine in 1987. From 2005 to 2010, he served as chief of the Division of Endocrinology and Metabolism. He took on the role of interim chair of the Department of Medicine upon Dr. Ken Kaushansky's departure in 2010. He was appointed Helen M. Ranney Professor and chair of the department in January of 2012 and is now Helen M. Ranney Distinguished Professor and Chair.