K21.9: Gastro-esophageal reflux disease without esophagitis

The ICD-10-CM code for GERD when the clinical record does not document associated esophagitis.

Billable

FY2027

TABLE OF CONTENTS

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At a glance

Code Family

K21: Gastro-esophageal reflux disease.

HCC Mapping (v28)

No HCC mapping: K21.9 does not map to any CMS-HCC v28 category.

Condition

GERD

Family Specificity

Three billable codes split by the presence or absence of esophagitis and, where esophagitis is present, by the presence or absence of bleeding.

Billable

Yes, valid for submission under FY2027, effective October 1, 2026.

Which K21 code do I assign?

The K21 family turns on two documented facts: whether esophagitis is present, and if it is, whether there is bleeding. K21.9 is the code for reflux disease with no esophagitis documented.

When documentation says…

Code

Reflux esophagitis with bleeding on endoscopy

K21.01

GERD with esophagitis, with bleeding. The note or endoscopy report must document both the esophagitis and the bleeding.

Erosive esophagitis, no bleeding

K21.00

GERD with esophagitis, without bleeding. Use when reflux esophagitis or erosive esophagitis is confirmed and no bleeding is documented. Update to this code after endoscopy confirms esophagitis.

GERD, no esophagitis documented

K21.9

GERD when no esophagitis is documented or confirmed, covering presentations where reflux symptoms are present but endoscopic or histologic esophagitis has not been identified or documented.

Tabular notes

EXCLUDES1

P78.83: Newborn esophageal reflux, from the Excludes1 note at category K21. An Excludes1 note means P78.83 and K21.9 are not reported together for the same condition.

NO USE ADDITIONAL OR CODE ALSO INSTRUCTIONS

K21.9 carries no Use Additional or Code Also notes. Additional codes may still be assigned for concurrent conditions when those are separately documented.

FY2027: EFFECTIVE 1 OCTOBER 2026

No codes were added to or deleted from category K21 in FY2026. No Excludes note changes were identified for K21.9 in the FY2026 tabular addenda. The FY2027 codes and tabular addenda make no addition, deletion or revision in category K21.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which code is selected.

CMS-HCC v28 (PY2024+)

K21.9 does not map to any Hierarchical Condition Category under CMS-HCC Model Version 28, which became fully operative at 100 percent for Medicare Advantage payment year 2026. GERD is not a risk-adjustment-bearing condition under the current CMS model. K21.9 generates no HCC risk adjustment weight.

COVERAGE CONTEXT

There is no National Coverage Determination specific to GERD diagnosis coding.

SEQUENCING

Sequence K21.9 as the principal or primary diagnosis only when GERD without esophagitis is the reason for the encounter. When GERD is incidental to another primary condition, sequence accordingly. Do not report K21.9 together with P78.83 for the same condition, which the Excludes1 note prohibits.

Documentation checklist to support K21.9

Chart elements that support code selection and reduce specificity-driven denials.

A documented diagnosis of GERD, gastroesophageal reflux disease, or gastric reflux.

No concurrent documentation of esophagitis: if esophagitis is confirmed, assign K21.00 without bleeding or K21.01 with bleeding instead.

A confirmed diagnosis for outpatient encounters. Possible or suspected GERD is not coded in the outpatient setting. Probable GERD documented at discharge may be coded on the inpatient side under UHDDS uncertain diagnosis guidelines.

Symptom documentation distinguished from a confirmed diagnosis, since heartburn or dyspepsia that is not confirmed as GERD belongs to R12 or R10.13.

A record review after any endoscopy. The code is updated to K21.00 or K21.01 when esophagitis is confirmed.

FAQ

Is K21.9 the right code for reflux or GERD without further specification?

Yes. When the provider documents GERD, gastroesophageal reflux, or acid reflux without specifying esophagitis, K21.9 is correct.

Do I need an endoscopy report to use K21.9?

No. GERD is a clinical diagnosis. K21.9 may be assigned on provider documentation alone, even without endoscopy, as long as no esophagitis is documented.

When should I not use K21.9?

Do not use it when esophagitis is documented, which calls for K21.00 or K21.01. For neonatal reflux, which is P78.83. For heartburn or dyspepsia that is not confirmed as GERD, which is R12 or R10.13. Or for eosinophilic esophagitis or other esophagitis not related to reflux, which fall under category K20, such as K20.0, K20.80 or K20.90.

Does K21.9 affect risk adjustment?

No. K21.9 does not map to any HCC under CMS-HCC v28. It carries no risk adjustment weight for Medicare Advantage payment year 2026.

Related codes

Codes in the same family as K21.9. Only codes with a published page render as links.

Sibling codes in the K21 family

K21.00: Gastro-esophageal reflux disease with esophagitis, without bleeding.
K21.01: Gastro-esophageal reflux disease with esophagitis, with bleeding.

Additional codes to consider

Codes outside the K21 family considered alongside K21.9.

Consider instead

P78.83: Newborn esophageal reflux.
K20.0: Eosinophilic esophagitis.
K20.80: Other esophagitis without bleeding, where the esophagitis is not related to reflux.
K20.90: Esophagitis, unspecified without bleeding, where the esophagitis is not related to reflux.
R12: Heartburn, the symptom code when GERD is not confirmed.
R10.13: Epigastric pain, which carries Dyspepsia as an inclusion term.

Sources

All claims on this page derive from government and professional-standards sources.

National Center for Health Statistics. (2026). International classification of diseases, tenth revision, clinical modification (ICD-10-CM) FY2027 files. https://www.cdc.gov/nchs/icd/icd-10-cm/files.html
Centers for Medicare & Medicaid Services and National Center for Health Statistics. (2026). ICD-10-CM official guidelines for coding and reporting FY2027. https://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10CM/2027/ICD-10-CM-October-1-2026-FY27-Guidelines.pdf
Centers for Medicare & Medicaid Services. (2025). 2026 model software/ICD-10 mappings. https://www.cms.gov/medicare/payment/medicare-advantage-rates-statistics/risk-adjustment/2026-model-software-icd-10-mappings
Centers for Medicare & Medicaid Services. (2026). MS-DRG classifications and software, version 44. https://www.cms.gov/medicare/payment/prospective-payment-systems/acute-inpatient-pps/ms-drg-classifications-and-software