2026 ICD-10-CM Diagnosis Code E66.2Morbid (severe) obesity with alveolar hypoventilation

ICD-10-CM Codes›E00–E89›E65-E68›E66

ICD-10-CM E66.2
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E66.2 is a billable ICD-10-CM diagnosis code for morbid (severe) obesity with alveolar hypoventilation. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 205 through 206. Coders also document this condition as alveolar hypoventilation. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Obesity.

Code Identity

ICD-10-CM Code
E66.2
Billable Status
Yes — Valid for Submission
Code Describes
Morbid (severe) obesity with alveolar hypoventilation
Short Description
Morbid (severe) obesity with alveolar hypoventilation
Same as the full description in the CMS dataset.
Parent Code
E66
Overweight and obesity

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE65-E68Overweight, obesity and other hyperalimentation
CategoryE66Overweight and obesity
This CodeE66.2Morbid (severe) obesity with alveolar hypoventilation

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Alveolar hypoventilation
  • Extreme obesity with alveolar hypoventilation
  • Morbid obesity

Tabular List NotesGuidance

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

Inclusion Terms

  • Obesity hypoventilation syndrome (OHS)
  • Pickwickian syndrome

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.

    • Obesity
      • with alveolar hypoventilation
    • Obesity
      • hypoventilation syndrome (OHS)
    • Obesity
      • morbid
        • with
          • alveolar hypoventilation
    • Obesity
      • morbid
        • with
          • obesity hypoventilation syndrome (OHS)
    • OHS(obesity hypoventilation syndrome)
    • Pickwickian syndrome
    • Syndrome
      • alveolar hypoventilation
    • Syndrome
      • cardiopulmonary-obesity
    • Syndrome
      • hypoventilation, obesity (OHS)
    • Syndrome
      • obesity hypoventilation (OHS)
    • Syndrome
      • Pickwickian

Clinical ClassificationClinical

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

CCSR END009
Obesity
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Morbid Obesity

    an excess of body weight, normally defined as an individual with a body mass index greater than 35 or a body weight greater than one hundred percent of ideal body weight.

Patient EducationClinical

Obesity

Obesity is a disease that means having too much body fat. It is different from being overweight, which means weighing too much. Both terms mean that your weight is greater than what's considered healthy for your height.

The full article covers:

  • What is obesity?
  • What raises your risk of obesity?
  • How is obesity diagnosed?
  • What health problems can obesity cause?
  • What are the treatments for obesity?

Read the full article at MedlinePlus

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

Convert E66.2 to ICD-9-CMHistory

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

ICD-9-CM
278.03 Obesity hypovent synd
Exact Match The mapping is direct, with no qualifiers.

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 E66.2Overview

Is E66.2 (Overweight and obesity) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report morbid (severe) obesity with alveolar hypoventilation on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E66.2 group to?

When morbid (severe) obesity with alveolar hypoventilation is the principal diagnosis on an inpatient stay, it groups to MS-DRG 205, 206, with relative weights from 0.9411 to 1.8310 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of E66.2?

Under the General Equivalence Mappings, morbid (severe) obesity with alveolar hypoventilation converts to ICD-9-CM 278.03 (obesity hypovent synd). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.