2026 ICD-10-CM Diagnosis Code I80.9Phlebitis and thrombophlebitis of unspecified site

ICD-10-CM Codes›I00–I99›I80-I89›I80

ICD-10-CM I80.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I80.9 is a billable ICD-10-CM diagnosis code for phlebitis and thrombophlebitis of unspecified site. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 299 through 301. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute phlebitis; thrombophlebitis and thromboembolism.

Code Identity

ICD-10-CM Code
I80.9
Billable Status
Yes — Valid for Submission
Code Describes
Phlebitis and thrombophlebitis of unspecified site
Short Description
Phlebitis and thrombophlebitis of unspecified site
Same as the full description in the CMS dataset.
Parent Code
I80
Phlebitis and thrombophlebitis

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI80-I89Diseases of veins, lymphatic vessels and lymph nodes, not elsewhere classified
CategoryI80Phlebitis and thrombophlebitis
This CodeI80.9Phlebitis and thrombophlebitis of unspecified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Deep thrombophlebitis
  • Endophlebitis
  • Periphlebitis
  • Phlebitis
  • Phlebitis after infusion
  • Phlebitis due to procedure
  • Phlebitis during procedure
  • Phlebitis following perfusion
  • Phlebitis following transfusion
  • Radiation thrombophlebitis
  • Septic thrombophlebitis
  • Sequela of phlebitis
  • Superficial thrombophlebitis
  • Superficial thrombophlebitis following administration of drug via intravenous route
  • Suppurative phlebitis
  • Thrombophlebitis
  • Thrombophlebitis after infusion
  • Thrombophlebitis due to procedure
  • Thrombophlebitis during procedure
  • Thrombophlebitis following perfusion
  • Thrombophlebitis following transfusion
  • Thrombophlebitis of the newborn

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.

    • Inflammation, inflamed, inflammatory(with exudation)
      • vein
        • thrombotic
    • Phlebitis(infective) (pyemic) (septic) (suppurative)
    • Phlebitis(infective) (pyemic) (septic) (suppurative)
      • ulcerative
    • Thrombophlebitis

Clinical ClassificationClinical

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

CCSR CIR033
Acute phlebitis; thrombophlebitis and thromboembolism
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Cavernous Sinus Thrombosis

    formation or presence of a blood clot (thrombus) in the cavernous sinus of the brain. infections of the paranasal sinuses and adjacent structures, craniocerebral trauma, and thrombophilia are associated conditions. clinical manifestations include dysfunction of cranial nerves iii, iv, v, and vi, marked periorbital swelling, chemosis, fever, and visual loss. (from adams et al., principles of neurology, 6th ed, p711)

  • Lateral Sinus Thrombosis

    formation or presence of a blood clot (thrombus) in the lateral sinuses. this condition is often associated with ear infections (otitis media or mastoiditis) without antibiotic treatment. in developed nations, lateral sinus thrombosis can result from craniocerebral trauma; brain neoplasms; neurosurgical procedures; thrombophilia; and other conditions. clinical features include headache; vertigo; and increased intracranial pressure.

  • Phlebitis

    inflammation of a vein, often a vein in the leg. phlebitis associated with a blood clot is called (thrombophlebitis).

  • Sagittal Sinus Thrombosis

    formation or presence of a blood clot (thrombus) in the superior sagittal sinus or the inferior sagittal sinus. sagittal sinus thrombosis can result from infections, hematological disorders, craniocerebral trauma; and neurosurgical procedures. clinical features are primarily related to the increased intracranial pressure causing headache; nausea; and vomiting. severe cases can evolve to seizures or coma.

  • Sinus Thrombosis, Intracranial

    formation or presence of a blood clot (thrombus) in the cranial sinuses, large endothelium-lined venous channels situated within the skull. intracranial sinuses, also called cranial venous sinuses, include the superior sagittal, cavernous, lateral, petrous sinuses, and many others. cranial sinus thrombosis can lead to severe headache; seizure; and other neurological defects.

  • Thrombophlebitis

    inflammation of a vein associated with a blood clot (thrombus).

Convert I80.9 to ICD-9-CMHistory

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

ICD-9-CM
451.9 Thrombophlebitis NOS
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 I80.9Overview

Is I80.9 (Phlebitis and thrombophlebitis) a billable code?

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

What MS-DRG does I80.9 group to?

When phlebitis and thrombophlebitis of unspecified site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 299, 300, 301, with relative weights from 0.7197 to 1.6327 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I80.9?

Under the General Equivalence Mappings, phlebitis and thrombophlebitis of unspecified site converts to ICD-9-CM 451.9 (thrombophlebitis NOS). The mapping is a direct match.

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.