Question 1

What is ICD-10 code Y63.6?

Accepted Answer

Y63.6 is the ICD-10-CM diagnosis code for underdosing and nonadministration of necessary drug, medicament or biological substance. A patient received less medication than prescribed or did not receive a necessary drug at all due to a medical error. Y63.6 sits in the ICD-10-CM chapter for external causes of morbidity (v00-y99), within the section covering misadventures to patients during surgical and medical care (y62-y69).

Y63.6 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 drug that was underdosed or not administered.

Question 2

Is Y63.6 an HCC code?

Accepted Answer

No. Y63.6 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is Y63.6 billable?

Accepted Answer

Yes. Y63.6 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. Y63.6 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for Y63.6?

Accepted Answer

Y63.6 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards Y63.6 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting Y63.6?

Accepted Answer

Document the specific drug that was underdosed or not administered This code indicates a patient safety event; ensure proper documentation of the error and any resulting harm

HCC Buddy Code Card

Y63.6

Is Y63.6 an HCC code?

What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Open Y63.6 in the Interactive Encoder

Y63.6 ICD-10-CM Code: Underdosing and nonadministration of necessary drug, medicament or biological substance

HCC Buddy Code Card

Y63.6

Is Y63.6 an HCC code?

What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Open Y63.6 in the Interactive Encoder