2026 ICD-10-CM Diagnosis Code Q21Congenital malformations of cardiac septa

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q21

ICD-10-CM Q21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q21 is a non-billable ICD-10-CM category code for congenital malformations of cardiac septa, so it cannot be submitted on claims. Use a more specific code from this category instead, such as Q21.0, Q21.10, Q21.11, and Q21.12.

Code Identity

ICD-10-CM Code
Q21
Billable Status
No — Non-Billable Category
Code Describes
Congenital malformations of cardiac septa
Chapter
Q20-Q28
Congenital malformations of the circulatory system

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ21Congenital malformations of cardiac septa
This CodeQ21Congenital malformations of cardiac septa

Specific Coding for Congenital malformations of cardiac septaOverview

Non-specific codes like Q21 require more characters. Use one of these billable codes instead:

  • Use Q21.0 for Ventricular septal defect

  • Q21.1 for Atrial septal defect

  • Use Q21.10 for Atrial septal defect, unspecified

  • Use Q21.11 for Secundum atrial septal defect

  • Use Q21.12 for Patent foramen ovale

  • Use Q21.13 for Coronary sinus atrial septal defect

  • Use Q21.14 for Superior sinus venosus atrial septal defect

  • Use Q21.15 for Inferior sinus venosus atrial septal defect

  • Use Q21.16 for Sinus venosus atrial septal defect, unspecified

  • Use Q21.19 for Other specified atrial septal defect

  • Q21.2 for Atrioventricular septal defect

  • Use Q21.20 for Atrioventricular septal defect, unspecified as to partial or complete

  • Use Q21.21 for Partial atrioventricular septal defect

  • Use Q21.22 for Transitional atrioventricular septal defect

  • Use Q21.23 for Complete atrioventricular septal defect

  • Use Q21.3 for Tetralogy of Fallot

  • Use Q21.4 for Aortopulmonary septal defect

  • Use Q21.8 for Other congenital malformations of cardiac septa

  • Use Q21.9 for Congenital malformation of cardiac septum, unspecified

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Type 1 Excludes

  • acquired cardiac septal defect I51.0

Patient EducationClinical

Congenital Heart Defects

Congenital heart defects (CHDs) are problems with the structure of the heart. "Congenital" means that that the problems are present at birth. These defects happen when a fetus's heart doesn't develop normally during pregnancy. Congenital heart defects are the most common type of birth defect.

The full article covers:

  • What are congenital heart defects?
  • What causes congenital heart defects?
  • Who is more likely to have a baby with a congenital heart defect?
  • What are the symptoms of congenital heart defects?
  • What other problems do congenital heart defects cause?
  • How are congenital heart defects diagnosed?
  • What are the treatments for congenital heart defects?

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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Q21Overview

Is Q21 (Congenital malformations of cardiac septa) a billable code?

No. This is a category header that groups the codes for congenital malformations of cardiac septa, and headers cannot be submitted on claims. Claims for congenital malformations of cardiac septa need a more specific code from this category, such as Q21.0, Q21.10, and Q21.11.