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ICD-10-CM 2027 diagnosis code

G44.021Chronic cluster headache, intractable

✓ Billable / specific

G44.021 is a valid, billable ICD-10-CM code for chronic cluster headache, intractable. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G44.021

G44.021 is the ICD-10-CM diagnosis code for chronic cluster headache, intractable. It belongs to category G44 (other headache syndromes), block G40-G47 (episodic and paroxysmal disorders) and chapter 6 (diseases of the nervous system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within G44.02 (chronic cluster headache), G44.021 is specifically for chronic cluster headache, intractable. Related codes cover not intractable (G44.029).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 102 (Headaches with MCC, relative weight 1.1201) and DRG 103 (Headaches without MCC, relative weight 0.822), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 339.02 (chronic cluster headache).

Notes that apply from higher levels

Instructions written at a parent level also apply to G44.021.

› From G44 Other headache syndromes
Excludes1
Excludes2
  • atypical facial pain (G50.1)
  • headache due to lumbar puncture (G97.1)
  • migraines (G43.-)
  • trigeminal neuralgia (G50.0)

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Alphabetic index entries

1 entries

Terms in the official ICD-10-CM index that lead to G44.021.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 01 · Diseases and Disorders of the Nervous System

ICD-9-CM equivalent

Converter →
  • 339.02Chronic cluster headacheapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about G44.021

Is G44.021 billable?

Yes. G44.021 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can G44.021 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict G44.021 as a principal diagnosis.

Is G44.021 a CC or MCC?

No. G44.021 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does G44.021 group to?

G44.021 is used in the MS-DRG v44.0 logic for MS-DRG 102 (Headaches with MCC) and MS-DRG 103 (Headaches without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for G44.021?

The CMS General Equivalence Mappings map G44.021 to ICD-9-CM 339.02.