After medical school there are several different routes to becoming an intensivist. One can do a three year internal medicine residency, and then a three year pulmonology/critical care fellowship, or a two year critical care fellowship. Also, if starting with internal medicine, it is possible to do a different specialty fellowship entirely, such as three years of cardiology of gastroenterology, and then an additional one year fellowship in critical care medicine.It is also possible to complete a residency first in general surgery, anesthesiology, and emergency medicine before applying for a 1-2 year fellowship in critical care.
