Z91.A3 — Caregiver's unintentional underdosing of patient's medication regimen
Is Z91.A3 billable?
Yes — Z91.A3 is billable for FY2027. Z91.A3 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. Z91.A3 may be submitted for encounters from October 1, 2026 through September 30, 2027.
Z91.A3 at a glance
| Code | Z91.A3 |
|---|---|
| Description | Caregiver's unintentional underdosing of patient's medication regimen |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
What Medicare edits apply to Z91.A3?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name Z91.A3 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.A3 group to?
Z91.A3 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.A3 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to Z91.A3. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Noncompliance › with › medication regimen NEC › underdosing › unintentional NEC › by caregiver
Code first
The underlying condition below must be sequenced before Z91.A3. Z91.A3 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.A3, but a patient may have both at the same time. When documentation supports it, Z91.A3 and the excluded code may both be reported.
Code also — inherited from Z77-Z99
Two codes may be needed to describe the condition fully. Whether Z91.A3 is sequenced first depends on the reason for the encounter.
- any follow-up examination (Z08-Z09)
How long has Z91.A3 existed?
Z91.A3 first appears in FY2023.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which conditions are coded to Z91.A3?
What other codes are in the Z91.A family? (5)
- Z91.A1Caregiver's noncompliance with patient's dietary regimennot billable
- Z91.A2Caregiver's intentional underdosing of patient's medication regimennot billable
- Z91.A4Caregiver's other noncompliance with patient's medication regimennot billable
- Z91.A5Caregiver's noncompliance with patient's renal dialysisnot billable
- Z91.A9Caregiver's noncompliance with patient's other medical treatment and regimennot billable