Z91.128 — Patient's intentional underdosing of medication regimen for other reason
Is Z91.128 billable?
Yes — Z91.128 is billable for FY2027. Z91.128 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. Z91.128 may be submitted for encounters from October 1, 2026 through September 30, 2027.
Z91.128 at a glance
| Code | Z91.128 |
|---|---|
| Description | Patient's intentional underdosing of medication regimen for other reason |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
What Medicare edits apply to Z91.128?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name Z91.128 directly.
CMS will reject this code as the principal diagnosis on an inpatient claim. It describes something other than the condition chiefly responsible for the admission.
Which MS-DRGs does Z91.128 group to?
Z91.128 sits in MDC 23 and helps define the logic of 1 MS-DRG (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 951Other Factors Influencing Health Statusmedical
How is Z91.128 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to Z91.128. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Underdosing › intentional NEC
- Noncompliance › with › medication regimen NEC › underdosing › intentional NEC
Code first — inherited from Z91.12
The underlying condition below must be sequenced before Z91.128. Z91.128 describes a manifestation and cannot be the principal or first-listed diagnosis.
- underdosing of medication (T36-T50) with fifth or sixth character 6
Excludes2 — not included here — inherited from Z91
The conditions below are not part of Z91.128, but a patient may have both at the same time. When documentation supports it, Z91.128 and the excluded code may both be reported.
Excludes2 — not included here — inherited from Z91.1
The conditions below are not part of Z91.128, but a patient may have both at the same time. When documentation supports it, Z91.128 and the excluded code may both be reported.
- caregiver noncompliance with patient's medical treatment and regimen (Z91.A-)
Code also — inherited from Z77-Z99
Two codes may be needed to describe the condition fully. Whether Z91.128 is sequenced first depends on the reason for the encounter.
- any follow-up examination (Z08-Z09)
Code also — inherited from Z91.1
Two codes may be needed to describe the condition fully. Whether Z91.128 is sequenced first depends on the reason for the encounter.
- , if applicable, to identify underdosing of specific drug (T36-T50 with final character 6)
How long has Z91.128 existed?
Z91.128 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.