Z91.A28
BillableCaregiver's intentional underdosing of medication regimen for other reason
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Z91.A28 an HCC code?
No. Z91.A28 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
Z91.A28 is the ICD-10-CM diagnosis code for caregiver's intentional underdosing of medication regimen for other reason. A caregiver is intentionally giving the patient less medication than prescribed for reasons other than financial hardship. Z91.A28 sits in the ICD-10-CM chapter for factors influencing health status and contact with health services (z00-z99), within the section covering persons with potential health hazards related to family and personal history and certain conditions influencing health status (z77-z99).
Z91.A28 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Document the specific reason for intentional underdosing (e.g., patient side effects, caregiver beliefs).
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Z91.A28 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the specific reason for intentional underdosing (e.g., patient side effects, caregiver beliefs).
- •Distinguish this from unintentional underdosing and from financial hardship-related underdosing.