ICD-10 Code I21.4 – Non-ST elevation (NSTEMI) myocardial infarction (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I21.4 – Non-ST elevation (NSTEMI) myocardial infarction
What it is
I21.4 identifies a myocardial infarction without ST elevation on the ECG. It is used when the record supports an acute NSTEMI rather than another type of acute coronary syndrome.
Clinical signs
Patients often present with chest discomfort, shortness of breath, diaphoresis, or nausea. Clinical features vary; refer to documentation, and confirm that the provider documents NSTEMI or non-ST elevation myocardial infarction.
When to use this code
Use I21.4 when the clinician clearly diagnoses an acute NSTEMI during the current episode of care. It is appropriate when documentation distinguishes this event from unstable angina, old infarction, or another MI type. Check documentation if the note is unclear.
Do not use for
Do not use I21.4 for unstable angina, prior history of MI, or a STEMI. If the chart only says “chest pain” or “possible MI,” do not assume NSTEMI without provider confirmation.
Coding tip
Code I21.4 only when the provider explicitly documents NSTEMI or non-ST elevation myocardial infarction.