The process for diagnosing mitochondrial diseases can be extensive and may involve a variety of testing. Usually doctors will gather your medical history, as well as perform a physical and neurological exam. Doctors may do a series of metabolic exams, which look at blood, urine or cerebral spinal fluid. They may perform a series of imaging tests, including MRIs and EKGs as well as eye and hearing exams, if necessary. Muscle biopsies may also be necessary. Finally additional blood work may be done for genetic testing. Sometimes, due to the complexity of the diseases, a definitive diagnosis may not be reached even after testing. The same mutation in mDNA may produce different symptoms depending on the organ the cells are in, complicating diagnosis.