2027 ICD-10-CM Diagnosis Code H49.21Sixth [abducent] nerve palsy, right eye

ICD-10-CM Codes›H00–H59›H49-H52›H49

ICD-10-CM H49.21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

H49.21 is a billable ICD-10-CM diagnosis code for sixth [abducent] nerve palsy, right eye. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 123. Coders also document this condition as right abducens nerve disorder. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neuro-ophthalmology and Strabismus.

Code Identity

ICD-10-CM Code
H49.21
Billable Status
Yes — Valid for Submission
Code Describes
Sixth [abducent] nerve palsy, right eye
Short Description
Sixth [abducent] nerve palsy, right eye
Same as the full description in the CMS dataset.
Parent Code
H49.2
Sixth [abducent] nerve palsy

Code Classification

ChapterH00–H59Diseases of the eye and adnexa
SectionH49-H52Disorders of ocular muscles, binocular movement, accommodation and refraction
CategoryH49Paralytic strabismus
This CodeH49.21Sixth [abducent] nerve palsy, right eye

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Right abducens nerve disorder

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to H49.21: its own notes plus those printed at H49, block H49-H52, and Chapter 7. A note printed at a category, block or chapter applies to every code under it.

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 H49 Paralytic strabismus applies to 29 codes
  • internal ophthalmoplegia (H52.51-)
  • internuclear ophthalmoplegia (H51.2-)
  • progressive supranuclear ophthalmoplegia (G23.1)
From Block H49-H52 Disorders of ocular muscles, binocular movement, accommodation and refraction applies to 150 codes
  • nystagmus and other irregular eye movements (H55)
From Chapter 7 (H00-H59) Diseases of the eye and adnexa applies to 2,677 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)
  • diabetes mellitus related eye conditions (E09.3-, E10.3-, E11.3-, E13.3-)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury (trauma) of eye and orbit (S05.-)
  • 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)
  • syphilis related eye disorders (A50.01, A50.3-, A51.43, A52.71)

Notes

General instructions on how these codes are used.

From Chapter 7 (H00-H59) Diseases of the eye and adnexa applies to 2,677 codes
  • Use an external cause code following the code for the eye condition, if applicable, to identify the cause of the eye condition

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name H49.21, its category, or a range that includes it.

Excludes2 1

These codes carry an Excludes2 note naming H49.21: its condition is not part of those codes, and both may be reported when the patient has both.

  • G52 Disorders of other cranial nerves
    paralytic strabismus due to nerve palsy (H49.0-H49.2) names H49.0-H49.2, which includes this code

Clinical ClassificationClinical

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

CCSR EYE006
Neuro-ophthalmology
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR EYE007
Strabismus
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Eye Movement Disorders

When you look at an object, you're using several muscles to move both eyes to focus on it. If you have a problem with the muscles, the eyes don't work properly.

Read the full article at MedlinePlus

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

Convert H49.21 to ICD-9-CMHistory

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

ICD-9-CM
378.54 Sixth nerve palsy
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 H49.21Overview

What is the ICD-10 code for sixth [abducent] nerve palsy, right eye?

The ICD-10-CM code for sixth [abducent] nerve palsy, right eye is H49.21 (sometimes written as H4921). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is H49.21 (Sixth [abducent] nerve palsy) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report sixth [abducent] nerve palsy, right eye on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does H49.21 group to?

When sixth [abducent] nerve palsy, right eye is the principal diagnosis on an inpatient stay, it groups to MS-DRG 123 (neurological Eye Disorders), which carries a relative weight of 0.8218. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of H49.21?

Under the General Equivalence Mappings, sixth [abducent] nerve palsy, right eye converts to ICD-9-CM 378.54 (sixth nerve palsy). The mapping is approximate, so confirm the match fits the documentation.