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Q21.3 — Tetralogy of Fallot
Q21.3
What this code means
Tetralogy of Fallot is a combination of four congenital heart defects causing reduced oxygen in the blood.
Also called: tetralogy of fallot, tof.
When this code is used
Used for tetralogy of Fallot.
Where it sits in ICD-10-CM
Code Q21.3 belongs to Chapter 17: Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders, which covers codes Q00–QA1 in the FY2027 ICD-10-CM tabular list. The official description above is copied verbatim from the CDC/NCHS FY2027 code file.
Related anatomy
Watch: related videos
Frequently asked questions
What is ICD-10-CM code Q21.3?
Q21.3 is the ICD-10-CM diagnosis code for “Tetralogy of Fallot”. Tetralogy of Fallot is a combination of four congenital heart defects causing reduced oxygen in the blood.
When is code Q21.3 used?
Used for tetralogy of Fallot. It belongs to Chapter 17 of ICD-10-CM (Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders).
This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.