CMS 1500 FORM Field 21 - Diagnosis or Nature of Illness or Injury

Field 21 - Diagnosis or Nature of Illness or Injury


The “ICD Indicator” identifies the version of the ICD code set being reported. The “Diagnosis or Nature of Illness or Injury” is the sign, symptom, complaint, or condition of the patient relating to the service(s) on the claim.

NUCC INSTRUCTIONS: Enter the applicable ICD indicator to identify which version of ICD codes is being reported.
9 ICD-9-CM
0 ICD-10-CM
Enter the indicator between the vertical, dotted lines in the upper right-hand area of the field.

Enter the codes left justified on each line to identify the patient’s diagnosis or condition. Do not include the decimal point in the diagnosis code, because it is implied. List no more than 12 ICD-10-CM or ICD-9-CM diagnosis codes. Relate lines A - L to the lines of service in 24E by the letter of the line. Use the greatest level of specificity. Do not provide narrative description in this field.

MEDICARE INSTRUCTIONS - Enter the patient's diagnosis/condition. With the exception of claims submitted by ambulance suppliers (specialty type 59), all physician and nonphysician specialties (i.e., PA, NP, CNS, CRNA) use diagnosis codes to the highest level of specificity for the date of service. Enter the diagnoses in priority order. All narrative diagnoses for nonphysician specialties shall be submitted on an attachment.

Reminder: Do not report ICD-10-CM codes for claims with dates of service prior to implementation of ICD-10-CM, on either the old or revised version of the CMS-1500 claim form.

For form version 08/05, report a valid ICD-9-CM code. Enter up to four diagnosis codes.

For form version 02/12, it may be appropriate to report either ICD-9-CM or ICD-10-CM codes depending upon the dates of service (i.e., according to the effective dates of the given code set).

• The “ICD Indicator” identifies the ICD code set being reported. Enter the applicable ICD indicator according to the following:

Enter the indicator as a single digit between the vertical, dotted lines.

• Do not report both ICD-9-CM and ICD-10-CM codes on the same claim form. If there are services you wish to report that occurred on dates when ICD-9-CM codes were in effect, and others that occurred on dates when ICD-10-CM codes were in effect, then send separate claims such that you report only ICD-9-CM or only ICD-10-CM codes on the claim. (See special considerations for spans of dates below.)

• If you are submitting a claim with a span of dates for a service, use the “from” date to determine which ICD code set to use.

• Enter up to 12 diagnosis codes. Note that this information appears opposite lines with letters A-L. Relate lines A- L to the lines of service in 24E by the letter of the line. Use the highest level of specificity. Do not provide narrative description in this field.

• Do not insert a period in the ICD-9-CM or ICD-10-CM code.

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