Is ICD-10-CM code K21 billable?

No, K21 (Gastro-esophageal reflux disease) is a non-billable ICD-10-CM code. It must be coded to a more specific subcategory before it can be used for reimbursement.

What chapter does ICD-10-CM code K21 belong to?

K21 belongs to Chapter 11 of the ICD-10-CM tabular list: K00–K95 (Diseases of the Digestive System).

K21Not billable, use a more specific code below

Gastro-esophageal reflux disease

In Diseases of esophagus, stomach and duodenum (K20-K31), chapter 11: Diseases of the Digestive System

3 billable codes under K21: 1 is an MCC; none map to an HCC.A CC or MCC (major CC) is a secondary diagnosis that raises the MS-DRG payment.

Instructional notes

Excludes1: not coded here, use a different code

newborn esophageal reflux (P78.83)

Also applies, from Diseases of esophagus, stomach and duodenum (K20-K31)

These notes sit on K20-K31 and apply to every code under it, including K21.

Excludes2: not included here, code separately if applicable

hiatus hernia (K44.-)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

There are no chapter-specific rules for Chapter 11 yet, so the general rules in Section I.B apply.

Read Section I.C.11 (page 58)

All codes under K21

K21 can't be used on a claim. Pick a billable code below; grey headings group them.

K21 MS-DRGs

As the principal diagnosis, the billable codes under K21 group to MS-DRG 391, 392, 368, 369, or 370 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

DRG 391 Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders with MCC (2 of 3 codes)
DRG 392 Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders without MCC (2 of 3 codes)
DRG 368 Major Esophageal Disorders with MCC (1 of 3 codes)
DRG 369 Major Esophageal Disorders with CC (1 of 3 codes)
DRG 370 Major Esophageal Disorders without CC/MCC (1 of 3 codes)

Other codes that refer to K21

Notes on these codes point to K21.

R63.31 Code Also: gastro-esophageal reflux disease (K21.-)
R63.32 Code Also: gastro-esophageal reflux disease (K21.-)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

GERD

Sometimes, after eating a large meal or lying down too soon after eating, you might feel acid coming up into your throat. This is called gastroesophageal reflux (GER). It happens when the muscle at the end of your esophagus (the tube that carries food from your mouth to your stomach) doesn't close properly. Stomach contents can then move back up and irritate the esophagus.

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.