I21 — Acute myocardial infarction

Not billable

Is I21 billable?

No — I21 is a non-billable header code. I21 groups more specific codes and cannot be submitted on a claim. A valid ICD-10-CM code must be reported at the highest level of specificity available in its branch. Select one of the 13 billable codes beneath I21.

Billable codes under this header

I21 at a glance

Code	I21
Description	Acute myocardial infarction
Billable	No — header code
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027

Use additional code

Report an additional code alongside I21 to fully describe the condition. I21 is sequenced first.

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)

Excludes2 — not included here

The conditions below are not part of I21, but a patient may have both at the same time. When documentation supports it, I21 and the excluded code may both be reported.

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

Includes

Conditions classified to I21.

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

Excludes2 — not included here — inherited from Chapter 9

The conditions below are not part of I21, but a patient may have both at the same time. When documentation supports it, I21 and the excluded code may both be reported.

certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
systemic connective tissue disorders (M30-M36)
transient cerebral ischemic attacks and related syndromes (G45.-)

Code also — inherited from I20-I25

Two codes may be needed to describe the condition fully. Whether I21 is sequenced first depends on the reason for the encounter.

the presence of hypertension (I10-I1A)

What codes fall under I21? (8)

How long has I21 existed?

I21 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.

Description changes

FY2018
ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction
Acute myocardial infarction

Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.

Which codes are confused with I21?

ICD-10-CM declares these codes mutually exclusive with I21 — exactly one of each pair can be correct for a given encounter.

vs I5ANon-ischemic myocardial injury (non-traumatic)