General Equivalence Mappings (GEMs)

Coding Corner

The information provided here applies to Medicare coding. Be sure to check with your Medicare Administrative Contractor (MAC) for additional information and clarification on these and other items. You should also contact your local insurance carriers to determine if private insurers follow Medicare's lead on all coding matters.

General Equivalence Mappings (GEMs)
CMS and the Centers for Disease Control and Prevention created the national version of the GEMs to ensure that consistency in national data is maintained. The GEMs are tools that act mainly as a crosswalk between the ICD-9 and ICD-10 codes, such that one can look up an ICD-9 code and be provided with the most appropriate ICD-10 matches and vice versa. They are not a substitute for learning the new ICD-10 codes; however, they can assist users with: translating lists of codes, code tables, or other coded data; converting a system or application containing ICD-9-CM codes; creating a “one-to-one” applied mapping (aka crosswalk) between code sets that will be used in an ongoing way to translate records or other coded data and studying the differences in meaning between the ICD-9-CM classification systems and the ICD-10-CM/PCS classification systems by looking at the GEMs entries for a given code or area of classification. For more information on GEMs, you may visit

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