What are medical ICD-9 codes?

ICD-9 medical codes are numeric and alphanumeric codes used for diagnosis, treatment and medical billing in the United States as of September 2015, explains MedicalBillingAndCoding.org. However, the United States is due to switch to ICD-10 on Oct. 1, 2015, as the American Medical Association points out.

The United States is the only country that still uses ICD-9 medical codes; the rest of the world has already switched to ICD-10, some as long as 10 years ago, according to MedicalBillingAndCoding.org. ICD-9 medical codes categorize illnesses, injuries or other medical conditions by category, breaking them into subcategories that specify the cause, site or manifestation of the condition when needed.