Most Social Security Disability cases turn on whether there are jobs available in the national economy that could be performed by the claimant, given his or her medical conditions. This requires a determination of the claimant’s Residual Functional Capacity (RFC). Social Security defines RFC as “the most you can do despite your limitations.”
In making this determination, someone has to translate medical conditions and associated symptoms to functional limitations. Clearly, the most appropriate person for this task is a doctor. At the Initial Application and Reconsideration levels a state employed doctor (Medical Consultant) makes this determination based on your medical records. Social Security might also send you to Consultative Exam (CE), where a specialist might provide insight into a particular part of your RFC, for example: If you allege both physical and mental impairments, but treat for your mental impairments with your primary doctor only, Social Security would likely send you to a CE with a psychologist.
 CFR § 416.945(a)(1).