2026 ICD-10-CM Diagnosis Code G47.12Idiopathic hypersomnia without long sleep time

ICD-10-CM Codes›G00–G99›G40-G47›G47

ICD-10-CM G47.12
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G47.12 is a billable ICD-10-CM diagnosis code for idiopathic hypersomnia without long sleep time. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as idiopathic hypersomnia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Sleep wake disorders.

Code Identity

ICD-10-CM Code
G47.12
Billable Status
Yes — Valid for Submission
Code Describes
Idiopathic hypersomnia without long sleep time
Short Description
Idiopathic hypersomnia without long sleep time
Same as the full description in the CMS dataset.
Parent Code
G47.1
Hypersomnia

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG40-G47Episodic and paroxysmal disorders
CategoryG47Sleep disorders
This CodeG47.12Idiopathic hypersomnia without long sleep time

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Idiopathic hypersomnia
  • Idiopathic hypersomnia without long sleep time
  • Primary hypersomnia

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.

    • Hypersomnia(organic)
      • idiopathic
        • without long sleep time

Clinical ClassificationClinical

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

CCSR NVS016
Sleep wake disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Idiopathic Hypersomnia

    a sleep disorder of central nervous system origin characterized by prolonged nocturnal sleep and periods of daytime drowsiness. affected individuals experience difficulty with awakening in the morning and may have associated sleep drunkenness, automatic behaviors, and memory disturbances. this condition differs from narcolepsy in that daytime sleep periods are longer, there is no association with cataplexy, and the multiple sleep latency onset test does not record sleep-onset rapid eye movement sleep. (from chokroverty, sleep disorders medicine, 1994, pp319-20; psychiatry clin neurosci 1998 apr:52(2):125-129)

  • Cataplexy

    a condition characterized by transient weakness or paralysis of somatic musculature triggered by an emotional stimulus or physical exertion. cataplexy is frequently associated with narcolepsy. during a cataplectic attack, there is a marked reduction in muscle tone similar to the normal physiologic hypotonia that accompanies rapid eye movement sleep (sleep, rem). (from adams et al., principles of neurology, 6th ed, p396)

Patient EducationClinical

Sleep Disorders

Sleep is a complex biological process. While you are sleeping, you are unconscious, but your brain and body functions are still active. They are doing a number of important jobs that help you stay healthy and function at your best. So when you don't get enough quality sleep, it does more than just make you feel tired.

The full article covers:

  • What is sleep?
  • What are sleep disorders?
  • What causes sleep disorders?
  • What are the symptoms of sleep disorders?
  • How are sleep disorders diagnosed?
  • What are the treatments for sleep disorders?

Read the full article at MedlinePlus

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

Convert G47.12 to ICD-9-CMHistory

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

ICD-9-CM
327.12 Idio hypersom-no lng slp
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 G47.12Overview

Is G47.12 (Hypersomnia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report idiopathic hypersomnia without long sleep time on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of G47.12?

Under the General Equivalence Mappings, idiopathic hypersomnia without long sleep time converts to ICD-9-CM 327.12 (idio hypersom-no lng slp). 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.