2026 ICD-10-CM Diagnosis Code Z91.128Patient's intentional underdosing of medication regimen for other reason

ICD-10-CM Codes›Z00–Z99›Z77-Z99›Z91

ICD-10-CM Z91.128
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z91.128 is a billable ICD-10-CM diagnosis code for Patient's intentional underdosing of medication regimen for other reason. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. Coders also document this condition as premedication deliberately omitted. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified status.

Code Identity

ICD-10-CM Code
Z91.128
Billable Status
Yes — Valid for Submission
Code Describes
Patient's intentional underdosing of medication regimen for other reason
Short Description
Patient's intentl undrdose of meds regimen for oth reason
Parent Code
Z91.12
Patient's intentional underdosing of medication regimen

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ77-Z99Persons with potential health hazards related to family and personal history and certain conditions influencing health status
CategoryZ91Personal risk factors, not elsewhere classified
This CodeZ91.128Patient's intentional underdosing of medication regimen for other reason

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z91.128.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Present on Admission (POA)Billing

Z91.128 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Premedication deliberately omitted

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.

    • Noncompliance
      • with
        • medication regimen NEC
          • underdosing
            • intentional NEC
    • Underdosing
      • intentional NEC

Clinical ClassificationClinical

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

CCSR FAC025
Other specified status
Default principal diagnosis: inpatient No · outpatient Yes

Patient EducationClinical

Medication Errors

Medicines treat infectious diseases, prevent problems from chronic diseases, and ease pain. But medicines can also cause harmful reactions if not used correctly. Errors can happen in the hospital, at the health care provider's office, at the pharmacy, or at home. You can help prevent errors by:

Read the full article at MedlinePlus

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

Convert Z91.128 to ICD-9-CMHistory

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

ICD-9-CM
V15.81 Hx of past noncompliance
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 Z91.128Overview

Is Z91.128 (Patient's intentional underdosing of medication regimen) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Patient's intentional underdosing of medication regimen for other reason on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Can Z91.128 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because Patient's intentional underdosing of medication regimen for other reason describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

Is Z91.128 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for Patient's intentional underdosing of medication regimen for other reason on inpatient claims.

What is the ICD-9 equivalent of Z91.128?

Under the General Equivalence Mappings, Patient's intentional underdosing of medication regimen for other reason converts to ICD-9-CM V15.81 (hx of past noncompliance). The mapping is approximate, so confirm the match fits the documentation.