2027 ICD-10-CM Diagnosis Code G44.001Cluster headache syndrome, unspecified, intractable

ICD-10-CM Codes›G00–G99›G40-G47›G44

ICD-10-CM G44.001
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G44.001 is a billable ICD-10-CM diagnosis code for cluster headache syndrome, unspecified, intractable. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 102 through 103. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Headache; including migraine.

Code Identity

ICD-10-CM Code
G44.001
Billable Status
Yes — Valid for Submission
Code Describes
Cluster headache syndrome, unspecified, intractable
Short Description
Cluster headache syndrome, unspecified, intractable
Same as the full description in the CMS dataset.
Parent Code
G44.00
Cluster headache syndrome, unspecified

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG40-G47Episodic and paroxysmal disorders
CategoryG44Other headache syndromes
This CodeG44.001Cluster headache syndrome, unspecified, intractable

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G44.001: its own notes plus those printed at G44 and Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From G44 Other headache syndromes applies to 40 codes

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From G44 Other headache syndromes applies to 40 codes
  • atypical facial pain (G50.1)
  • headache due to lumbar puncture (G97.1)
  • migraines (G43.-)
  • trigeminal neuralgia (G50.0)
From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G44.001, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G44.001: they are not reported together with it, unless the two conditions are unrelated.

  • G43 Migraine
    lower half migraine (G44.00) names G44.00, which includes this code

Excludes2 4

These codes carry an Excludes2 note naming G44.001: its condition is not part of those codes, and both may be reported when the patient has both.

  • G43 Migraine
    headache syndromes (G44.-) names G44.-, which includes this code
  • G44.1 Vascular headache, not elsewhere classified
    cluster headache (G44.0) names G44.0, which includes this code
  • G89 Pain, not elsewhere classified
    headache syndromes (G44.-) names G44.-, which includes this code
  • R51 Headache
    migraine and other headache syndromes (G43-G44) names G43-G44, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR NVS010
Headache; including migraine
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Cluster Headache

    a primary headache disorder that is characterized by severe, strictly unilateral pain which is orbital, supraorbital, temporal or in any combination of these sites, lasting 15-180 min. occurring 1 to 8 times a day. the attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, facial sweating, eyelid edema, and miosis. (international classification of headache disorders, 2nd ed. cephalalgia 2004: suppl 1)

Patient EducationClinical

Headache

Almost everyone has had a headache. Headache is the most common form of pain. It's a major reason people miss days at work or school or visit the doctor.

Read the full article at MedlinePlus

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

Convert G44.001 to ICD-9-CMHistory

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

ICD-9-CM
339.00 Cluster headache syn NOS
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G44.001Overview

What is the ICD-10 code for cluster headache syndrome, unspecified, intractable?

The ICD-10-CM code for cluster headache syndrome, unspecified, intractable is G44.001 (sometimes written as G44001). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G44.001 (Cluster headache syndrome, unspecified) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report cluster headache syndrome, unspecified, intractable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G44.001 group to?

When cluster headache syndrome, unspecified, intractable is the principal diagnosis on an inpatient stay, it groups to MS-DRG 102, 103, with relative weights from 0.8219 to 1.1200 depending on complications. Higher weights mean higher Medicare reimbursement.

Can G44.001 be reported with R51.9?

Not as a rule. The Excludes1 note at G44, which applies to G44.001, lists "headache NOS (R51.9)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of G44.001?

Under the General Equivalence Mappings, cluster headache syndrome, unspecified, intractable converts to ICD-9-CM 339.00 (cluster headache syn NOS). The mapping is approximate, so confirm the match fits the documentation.