2026 ICD-10-CM Diagnosis Code I80.299Phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity

ICD-10-CM Codes›I00–I99›I80-I89›I80

ICD-10-CM I80.299
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I80.299 is a billable ICD-10-CM diagnosis code for phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity. 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. The code is flagged as an unspecified code, since codes identifying laterality exist in the same family. Coders also document this condition as thrombophlebitis of superficial veins of lower extremity. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute phlebitis; thrombophlebitis and thromboembolism.

Code Identity

ICD-10-CM Code
I80.299
Billable Status
Yes — Valid for Submission
Code Describes
Phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity
Short Description
Phlebitis and thombophlb of deep vessels of unsp low extrm
Parent Code
I80.29
Phlebitis and thrombophlebitis of other deep vessels of lower extremities

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI80-I89Diseases of veins, lymphatic vessels and lymph nodes, not elsewhere classified
CategoryI80Phlebitis and thrombophlebitis
This CodeI80.299Phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity

Code EditsBilling

Medicare Code Editor checks that affect claim validity for I80.299.

Unspecified codes
Unspecified codes exist in the ICD-10-CM classification for circumstances when documentation in the medical record does not provide the level of detail needed to support reporting a more specific code. However, in the inpatient setting, there should generally be very limited and rare circumstances for which the laterality (right, left, bilateral) of a condition is unable to be documented and reported. The following pages contain the list of unspecified ICD-10-CM diagnosis codes for which there is a more specific code to identify laterality (right, left, bilateral) within that code family.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Thrombophlebitis of superficial veins of lower extremity

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.

    • Thrombophlebitis
      • lower extremity

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

Patient EducationClinical

Deep Vein Thrombosis

Deep vein thrombosis, or DVT, is a blood clot that forms in a vein deep in the body. Most deep vein clots occur in the lower leg or thigh. If the vein swells, the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a serious problem in the lung, called a pulmonary embolism.

Read the full article at MedlinePlus

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

Convert I80.299 to ICD-9-CMHistory

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

ICD-9-CM
451.19 Deep phlebitis-leg NEC
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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About I80.299Overview

Is I80.299 a billable code?

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

What MS-DRG does I80.299 group to?

When phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity 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 I80.299?

Under the General Equivalence Mappings, phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity converts to ICD-9-CM 451.19 (deep phlebitis-leg NEC). The mapping is approximate, so confirm the match fits the documentation.

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.