What are medical billing diagnosis codes?

The health care field uses diagnosis codes for billing and for providing accurate documentation of a patient's diagnosis and treatment, acccording to Medical Billing and Coding. The World Health Organization developed the International Classification of Diseases as a systematic way for health care providers to keep accurate documentation.

Each medical condition, injury and disease has an assigned ICD code. The diagnosis code offers justification for any testing, treatment or procedure subsequently ordered by the treating physician. Insurance companies use the diagnosis and procedure codes to provide proper financial reimbursement to doctors and hospitals. The Centers for Medicare and Medicaid Services website provides a listing of all ICD codes that are used in the United States as of 2015.