I21.3: ST elevation (STEMI) myocardial infarction of unspecified site
I21.3 is the billable ICD-10-CM diagnosis code for ST elevation (STEMI) myocardial infarction of unspecified site. It is a fully specified code, so it can be reported on a claim (subject to clinical documentation and your payer's rules).
Frequently asked questions
What is ICD-10-CM code I21.3?
I21.3 is the ICD-10-CM diagnosis code for ST elevation (STEMI) myocardial infarction of unspecified site. It belongs to category I21 (Acute myocardial infarction).
Is I21.3 a billable code?
Yes. I21.3 is a billable, fully specified ICD-10-CM code, so it can be used on a claim (subject to documentation and payer rules).
What category does I21.3 belong to?
I21.3 is part of ICD-10-CM category I21 — Acute myocardial infarction, which has 26 billable codes.
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Informational only, not coding or medical advice. Verify against the official ICD-10-CM (FY2026) and your payer's guidelines.
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