2026 ICD-10-CM Diagnosis Code R79.81Abnormal blood-gas level

ICD-10-CM Codes›R00–R99›R70-R79›R79

ICD-10-CM R79.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R79.81 is a billable ICD-10-CM diagnosis code for abnormal blood-gas level. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 947 through 948. As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Abnormal findings without diagnosis.

Code Identity

ICD-10-CM Code
R79.81
Billable Status
Yes — Valid for Submission
Code Describes
Abnormal blood-gas level
Short Description
Abnormal blood-gas level
Same as the full description in the CMS dataset.
Parent Code
R79.8
Other specified abnormal findings of blood chemistry

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR70-R79Abnormal findings on examination of blood, without diagnosis
CategoryR79Other abnormal findings of blood chemistry
This CodeR79.81Abnormal blood-gas level

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abnormal blood oxygen pressure
  • Arterial blood gas outside reference range
  • Arterial blood pH outside reference range
  • Arterial carbon dioxide outside reference range
  • Arterial partial pressure of carbon dioxide above reference range
  • Arterial partial pressure of carbon dioxide below reference range
  • Blood gases outside reference range
  • Blood oxygen concentration below reference range
  • Blood oxygen level outside reference range
  • Finding of arterial blood pH
  • Finding of arterial partial pressure of carbon dioxide
  • Finding of oxygen saturation
  • Finding of venous blood pH
  • Hypocapnia
  • Oxygen saturation above reference range
  • Oxygen saturation below reference range
  • Oxygen saturation in arterial blood above reference range
  • Venous blood pH outside reference range

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Abnormal, abnormality, abnormalities
      • blood-gas level
    • Abnormal, abnormality, abnormalities
      • chemistry, blood
        • gas level

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR SYM017
Abnormal findings without diagnosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Hypocapnia

    clinical manifestation consisting of a deficiency of carbon dioxide in arterial blood.

Patient EducationClinical

Blood

Your blood is made up of liquid and solids. The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert R79.81 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
790.91 Abnrml art blood gases
Approximate The match is approximate rather than exact.

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 R79.81Overview

Is R79.81 (Other specified abnormal findings of blood chemistry) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report abnormal blood-gas level on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does R79.81 group to?

When abnormal blood-gas level is the principal diagnosis on an inpatient stay, it groups to MS-DRG 947, 948, with relative weights from 0.8005 to 1.2694 depending on complications. Higher weights mean higher Medicare reimbursement.

Can R79.81 be a principal diagnosis?

Use it with care. This is a symptom code, so once a definitive diagnosis explaining the abnormal blood-gas level is established, that condition takes the principal position instead.

What is the ICD-9 equivalent of R79.81?

Under the General Equivalence Mappings, abnormal blood-gas level converts to ICD-9-CM 790.91 (abnrml art blood gases). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.