2026 ICD-10-CM Diagnosis Code R51.9Headache, unspecified

ICD-10-CM Codes›R00–R99›R50-R69›R51

ICD-10-CM R51.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R51.9 is a billable ICD-10-CM diagnosis code for headache, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 102 through 103. As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Headache; including migraine and Nervous system signs and symptoms.

This medical diagnosis code is frequently used in Family Practice medical specialties to designate conditions such headache.

Code Identity

ICD-10-CM Code
R51.9
Billable Status
Yes — Valid for Submission
Code Describes
Headache, unspecified
Short Description
Headache, unspecified
Same as the full description in the CMS dataset.
Parent Code
R51
Headache

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR50-R69General symptoms and signs
CategoryR51Headache
This CodeR51.9Headache, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Aching headache
  • Acute headache
  • Acute pain in face
  • Aural headache
  • Bilateral headache
  • Chronic daily headache
  • Chronic orofacial pain
  • Chronic orofacial pain due to disorder
  • Chronic orofacial pain due to infectious disease
  • Chronic orofacial pain due to nonvascular intracranial disorder
  • Chronic orofacial pain due to temporomandibular joint disorder
  • Chronic pain in face
  • Chronic primary orofacial pain
  • Chronic secondary facial pain
  • Craniofacial pain
  • Daily headache
  • Delayed headache caused by alcohol
  • Dental headache
  • Effects of high altitude
  • Frequent headache
  • Frontal headache
  • Frontal sinus pain
  • Generalized headache
  • Headache
  • Headache caused by carbon monoxide
  • Headache caused by high altitude
  • Headache caused by monosodium glutamate
  • Headache character - finding
  • Headache disorder
  • Headache due to acute angle closure glaucoma
  • Headache due to arterial hypertension
  • Headache due to cold exposure
  • Headache due to external compression of head
  • Headache due to intracranial disease
  • Headache due to intracranial neoplasm
  • Headache due to reversible cerebral vasoconstriction syndrome
  • Headache due to spontaneous subarachnoid hemorrhage
  • Headache following myelography
  • Heavy head
  • Hindbrain hernia headache
  • Intermittent headache
  • Intolerance to monosodium glutamate
  • Low pressure headache
  • Maxillary sinus pain
  • Morning headache
  • Muscular headache
  • Nasal headache
  • Obstetric spinal and epidural anesthesia-induced headache
  • Occipital headache
  • Pain due to neoplastic disease
  • Pain in cheek
  • Pain in chin
  • Pain in face
  • Pain of head and neck region
  • Pain radiating to head
  • Parietal headache
  • Post dural puncture headache
  • Post-ictal state
  • Postpartum headache
  • Postseizure headache
  • Referred pain
  • Referred pain in face
  • Shooting headache
  • Shooting pain
  • Sinus headache
  • Temporal headache
  • Tenderness of face
  • Tenderness of head and neck region
  • Tenderness of neck
  • Tenderness of respiratory structure
  • Tenderness of scalp
  • Tenderness over frontal sinus
  • Tenderness over maxillary sinus
  • Throbbing headache
  • Throbbing pain
  • Unilateral headache
  • Unilateral left sided headache
  • Unilateral right sided headache
  • Viral headache

Tabular List NotesGuidance

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

Inclusion Terms

  • Facial pain NOS

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.

    • Headache
    • Headache
      • chronic daily
    • Headache
      • daily chronic
    • Headache
      • nasal septum
    • Pain(s)
      • face, facial

Clinical ClassificationClinical

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

CCSR NVS010
Headache; including migraine
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR SYM010
Nervous system signs and symptoms
Default principal diagnosis: inpatient No · outpatient No

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)

  • Headache

    the symptom of pain in the cranial region. it may be an isolated benign occurrence or manifestation of a wide variety of headache disorders.

  • Headache Disorders

    various conditions with the symptom of headache. headache disorders are classified into major groups, such as primary headache disorders (based on characteristics of their headache symptoms) and secondary headache disorders (based on their etiologies). (international classification of headache disorders, 2nd ed. cephalalgia 2004: suppl 1)

  • Headache Disorders, Primary

    conditions in which the primary symptom is headache and the headache cannot be attributed to any known causes.

  • Headache Disorders, Secondary

    conditions with headache symptom that can be attributed to a variety of causes including brain vascular disorders; wounds and injuries; infection; drug use or its withdrawal.

  • Migraine Disorders

    a class of disabling primary headache disorders, characterized by recurrent unilateral pulsatile headaches. the two major subtypes are common migraine (without aura) and classic migraine (with aura or neurological symptoms). (international classification of headache disorders, 2nd ed. cephalalgia 2004: suppl 1)

  • Post-Dural Puncture Headache

    a secondary headache disorder attributed to low cerebrospinal fluid pressure caused by spinal puncture, usually after dural or lumbar puncture.

  • Post-Traumatic Headache

    secondary headache attributed to trauma of the head and/or the neck.

  • Tension-Type Headache

    a common primary headache disorder, characterized by a dull, non-pulsatile, diffuse, band-like (or vice-like) pain of mild to moderate intensity in the head; scalp; or neck. the subtypes are classified by frequency and severity of symptoms. there is no clear cause even though it has been associated with muscle contraction and stress. (international classification of headache disorders, 2nd ed. cephalalgia 2004: suppl 1)

  • Vascular Headaches

    secondary headache disorders attributed to a variety of cranial or cervical vascular disorders, such as brain ischemia; intracranial hemorrhages; and central nervous system vascular malformations.

  • SF-MPQ-2 - Shooting Pain|SFMP2-Shooting Pain|SFMP2-Shooting Pain|SFMP202

    short-form mcgill pain questionnaire-2 (short form mpq) shooting pain.

  • Shooting Pain

    an intense sensation of discomfort or distress that radiates from one location to another sharply.

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.

Code History & ChangesHistory

Replacement R51.9 replaces the following previously assigned code(s):

  • R51 - Headache
FY 2021AddedAdded to the ICD-10-CM code setEffective October 1, 2020.
FY 2022–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About R51.9Overview

Is R51.9 (Headache) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report headache, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does R51.9 group to?

When headache, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 102, 103, with relative weights from 0.8363 to 1.1209 depending on complications. Higher weights mean higher Medicare reimbursement.

Can R51.9 be a principal diagnosis?

Use it with care. This is a symptom code, so once a definitive diagnosis explaining the headache, unspecified is established, that condition takes the principal position instead.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.