Is I21 a billable ICD-10-CM code?

No. I21 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does I21 sit in the tabular list?

Diseases of the circulatory system (I00-I99), in the block Ischemic heart diseases (I20-I25).

I21

I21 — Acute myocardial infarction

Non-billable headerICD-10-CM

I21 is a non-billable header ICD-10-CM code for acute myocardial infarction. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes2 — not included here, but may coexist

The excluded condition is not part of this code, but a patient can have both. You may code both.

old myocardial infarction (I25.2)
postmyocardial infarction syndrome (I24.1)
subsequent type 1 myocardial infarction (I22.-)

Use additional code

Add a secondary code to capture the detail described below.

code, if applicable, to identify:
exposure to environmental tobacco smoke (Z77.22)
history of tobacco dependence (Z87.891)
occupational exposure to environmental tobacco smoke (Z57.31)
status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)
tobacco dependence (F17.-)
tobacco use (Z72.0)

Includes

Conditions this code covers.

cardiac infarction
coronary (artery) embolism
coronary (artery) occlusion
coronary (artery) rupture
coronary (artery) thrombosis
infarction of heart, myocardium, or ventricle
myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onset

Other codes that can never be billed with I21

These codes carry an Excludes1 note pointing at I21. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading I21 alone.

I22Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction
I24.8Other forms of acute ischemic heart disease
I25.82Chronic total occlusion of coronary artery
I5ANon-ischemic myocardial injury (non-traumatic)

Risk adjustment

I21 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code to one of these instead I21

8 child codes. Green means billable.

Questions about I21

Is I21 a billable ICD-10-CM code?: No. I21 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does I21 sit in the tabular list?: Diseases of the circulatory system (I00-I99), in the block Ischemic heart diseases (I20-I25).