Billable / Specific Code
ICD-10-CM I21.3 is the diagnosis code for ST elevation (STEMI) myocardial infarction of unspecified site. This code falls under the section "Ischemic heart diseases" within Chapter 9 — Diseases of the circulatory system (I00-I99). It is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. Medical coders and healthcare providers use this code to document and classify diagnoses in electronic health records, insurance claims, and clinical databases.
Understanding where I21.3 sits in the ICD-10-CM classification helps ensure proper coding:
Yes, I21.3 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
I21.3 is the ICD-10-CM diagnosis code for "ST elevation (STEMI) myocardial infarction of unspecified site". It is used by healthcare providers to classify and document this condition in medical records and insurance claims.
The parent code of I21.3 is I21 ("Acute myocardial infarction"). I21.3 provides a more specific classification within this category.
I21.3 is located in Section I20-I25 — "Ischemic heart diseases" within Chapter 9 of the ICD-10-CM Tabular List.
Use I21.3 when the patients documented diagnosis matches "ST elevation (STEMI) myocardial infarction of unspecified site" and the clinical documentation supports this level of specificity. Always verify with the latest ICD-10-CM guidelines and payer requirements.
The ICD-10-CM code for ST elevation (STEMI) myocardial infarction of unspecified site is I21.3.
Yes, I21.3 can be used as a primary diagnosis code since it is billable and specific.
I21.3 is in Chapter 9 of the ICD-10-CM Tabular List.
Yes, I21.3 is a valid ICD-10-CM code for the 2026 fiscal year, subject to official CMS updates.