2026 ICD-10-CM Diagnosis Code I15.9Secondary hypertension, unspecified

ICD-10-CM Codes›I00–I99›I10-I1A›I15

ICD-10-CM I15.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I15.9 is a billable ICD-10-CM diagnosis code for secondary hypertension, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 304 through 305. Coders also document this condition as diastolic hypertension. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Hypertension with complications and secondary hypertension.

Code Identity

ICD-10-CM Code
I15.9
Billable Status
Yes — Valid for Submission
Code Describes
Secondary hypertension, unspecified
Short Description
Secondary hypertension, unspecified
Same as the full description in the CMS dataset.
Parent Code
I15
Secondary hypertension

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI10-I1AHypertensive diseases
CategoryI15Secondary hypertension
This CodeI15.9Secondary hypertension, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Diastolic hypertension
  • Hypertensive crisis
  • Hypertensive emergency
  • Malignant hypertension
  • Malignant secondary hypertension
  • Paroxysmal hypertension
  • Perioperative hypertension
  • Pre-existing secondary hypertension complicating pregnancy, childbirth and puerperium
  • Secondary diastolic hypertension
  • Secondary hypertension

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.

    • Hypertension, hypertensive(accelerated) (benign) (essential) (idiopathic) (malignant) (systemic)
      • secondary NEC

Clinical ClassificationClinical

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

CCSR CIR008
Hypertension with complications and secondary hypertension
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Hypertensive Crisis

    a severe, acute increase in blood pressure that may result in stroke or myocardial ischemia.

  • Paroxysmal Hypertension

    hypertension that presents intermittently.

  • Diastolic Hypertension

    hypertension characterized diastolic blood pressure greater than 90 mmhg on two occasions.

  • Malignant Hypertension

    severe hypertension that is characterized by rapid onset of extremely high blood pressure.

Patient EducationClinical

High Blood Pressure

Blood pressure is the force of your blood pushing against the walls of your arteries. Each time your heart beats, it pumps blood into the arteries. Your blood pressure is highest when your heart beats, pumping the blood. This is called systolic pressure. When your heart is at rest, between beats, your blood pressure falls.

The full article covers:

  • What is blood pressure?
  • How is high blood pressure diagnosed?
  • What are the different types of high blood pressure?
  • Why do I need to worry about high blood pressure?
  • What are the treatments for high blood pressure?

Read the full article at MedlinePlus

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

Convert I15.9 to ICD-9-CMHistory

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

ICD-9-CM
405.99 Second hypertension 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 I15.9Overview

Is I15.9 (Secondary hypertension) a billable code?

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

What MS-DRG does I15.9 group to?

When secondary hypertension, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 304, 305, with relative weights from 0.7551 to 1.1900 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I15.9?

Under the General Equivalence Mappings, secondary hypertension, unspecified converts to ICD-9-CM 405.99 (second hypertension NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.