A nephrologist is a physician who has been trained in the diagnosis and management of kidney disease, kidney transplantation, therapy of high blood pressure, and dialysis. Nephrology is a subspecialty of internal medicine. In the United States, after medical school nephrologists complete a three year residency in internal medicine followed by a two year (or longer) fellowship in nephrology.

Knowledge of internal medicine is required to obtain certification. To become a nephrologist requires many years of school and training. Nephrologists also must be approved by the board. To be approved, the physician must fulfill the requirements for education and training in nephrology in order to qualify to take the board's examination. If a physician passes the examination, then he or she can become a nephrology specialist. Typically, nephrologists also need two to three years of training in an ACGME accredited program in nephrology. Things that a nephrologist learns in this program are fluid and acid base and electrolyte physiology, medical management of acute and chronic renal failure, glomerular and casuclar disorders, tubular/interstitial disorders, mineral metabolism, clinical pharmacology, hypertension, epidemiology, thics, and nutrition. Once training is satisfactorily completed, the physician is eligible to take the ABIM nephrology examination.

Nephrologists may further specialize in pediatric nephrology (treatment of kidney diseases in children) or adult nephrology. Certification in these subspecialties requires satisfactory completion of additional education and training and passing an examination.