2027 ICD-10-CM Diagnosis Code I21Acute myocardial infarction

ICD-10-CM Codes›I00–I99›I20-I25›I21

ICD-10-CM I21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I21 is a non-billable ICD-10-CM category code for acute myocardial infarction, so it cannot be submitted on claims. Use a more specific code from this category instead, such as I21.01, I21.02, I21.09, and I21.11.

Code Identity

ICD-10-CM Code
I21
Billable Status
No — Non-Billable Category
Code Describes
Acute myocardial infarction
Short Description
Acute myocardial infarction
Same as the full description in the CMS dataset.
Chapter
I20-I25
Ischemic heart diseases

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI20-I25Ischemic heart diseases
CategoryI21Acute myocardial infarction
This CodeI21Acute myocardial infarction

Specific Coding for Acute myocardial infarctionOverview

Non-specific codes like I21 require more characters. Use one of these billable codes instead:

  • I21.0 for ST elevation (STEMI) myocardial infarction of anterior wall

  • Use I21.01 for ST elevation (STEMI) myocardial infarction involving left main coronary artery

  • Use I21.02 for ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery

  • Use I21.09 for ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall

  • I21.1 for ST elevation (STEMI) myocardial infarction of inferior wall

  • Use I21.11 for ST elevation (STEMI) myocardial infarction involving right coronary artery

  • Use I21.19 for ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall

  • I21.2 for ST elevation (STEMI) myocardial infarction of other sites

  • Use I21.21 for ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery

  • Use I21.29 for ST elevation (STEMI) myocardial infarction involving other sites

  • Use I21.3 for ST elevation (STEMI) myocardial infarction of unspecified site

  • Use I21.4 for Non-ST elevation (NSTEMI) myocardial infarction

  • Use I21.9 for Acute myocardial infarction, unspecified

  • I21.A for Other type of myocardial infarction

  • Use I21.A1 for Myocardial infarction type 2

  • Use I21.A9 for Other myocardial infarction type

  • Use I21.B for Myocardial infarction with coronary microvascular dysfunction

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I21: its own notes plus those printed at block I20-I25 and Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

  • 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: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

On I21 itself
  • old myocardial infarction (I25.2)
  • postmyocardial infarction syndrome (I24.1)
  • subsequent type 1 myocardial infarction (I22.-)
From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • 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.-)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

  • 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)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Block I20-I25 Ischemic heart diseases applies to 94 codes
  • the presence of hypertension (I10-I1A)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I21, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming I21: they are not reported together with it, unless the two conditions are unrelated.

  • I5A Non-ischemic myocardial injury (non-traumatic)
    acute myocardial infarction (I21.-)

Excludes2 2

These codes carry an Excludes2 note naming I21: its condition is not part of those codes, and both may be reported when the patient has both.

  • I74 Arterial embolism and thrombosis
    coronary embolism and thrombosis (I21-I25)
  • I82 Other venous embolism and thrombosis
    coronary (I21-I25)

Code First 1

These codes say to code first a condition named in the note, and I21 is one of the conditions named.

  • Z92.82 Status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility
    acute myocardial infarction (I21.-, I22.-)

Code Also 1

These codes say I21 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • I16.1 Hypertensive emergency
    acute myocardial infarction (I21.-)

Clinical InformationClinical

  • Acute Myocardial Infarction

    necrosis of the myocardium, as a result of interruption of the blood supply to the area. it is characterized by a severe and rapid onset of symptoms that may include chest pain, often radiating to the left arm and left side of the neck, dyspnea, sweating, and palpitations.

Patient EducationClinical

Heart Attack

A heart attack, also called a myocardial infarction, is a type of heart disease. It happens when blood flow to the heart suddenly becomes blocked. Without the blood coming in, the heart can't get oxygen. If not treated quickly, the heart muscle begins to die.

The full article covers:

  • What is a heart attack?
  • What heart attack risk factors can be changed?
  • What heart attack risk factors can't be changed?
  • What causes a heart attack?
  • What are the symptoms of a heart attack?
  • How is a heart attack diagnosed?
  • What is the treatment for a heart attack?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I21Overview

What is the ICD-10 code for acute myocardial infarction?

I21 is the ICD-10-CM category for acute myocardial infarction, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is I21 (Acute myocardial infarction) a billable code?

No. This is a category header that groups the codes for acute myocardial infarction, and headers cannot be submitted on claims. Claims for acute myocardial infarction need a more specific code from this category, such as I21.01, I21.02, and I21.09.

Does I21 need an additional code?

When the condition applies, yes. The Use Additional Code note reads: 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.-); and 1 more listed in the Instructional Notes section. The additional code is reported after I21.