Z79.631 ICD-10-CM Code: Long term (current) use of antimetabolite agent
Z79.631 is not a CMS-HCC payment code. MEAT criteria · RAF calculator · HCC Buddy coding tools
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FY 2026 Apr update / Factors influencing health status and contact with health services (Z00-Z99) / Persons with potential health hazards related to family and personal history and certain conditions influencing health status (Z77-Z99)
Z79.631
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceLong term (current) use of antimetabolite agent
A patient is currently taking an antimetabolite agent, a chemotherapy drug that interferes with cancer cell metabolism and DNA synthesis.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Long term (current) use of 5-fluorouracil
- Long term (current) use of 6-mercaptopurine
- Long term (current) use of cytarabine
- Long term (current) use of methotrexate
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for Z79.631 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for Z79.631 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for Z79.631 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for Z79.631 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for Z79.631 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for Z79.631 in this effective period.
Buddy Documentation Tip
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is Z79.631 an HCC code?
No. Z79.631 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
- Code
- Z79.631
- Description
- Long term (current) use of antimetabolite agent
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
Z79.631 is the ICD-10-CM diagnosis code for long term (current) use of antimetabolite agent. A patient is currently taking an antimetabolite agent, a chemotherapy drug that interferes with cancer cell metabolism and DNA synthesis. Z79.631 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).
Z79.631 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.
Use for medications like methotrexate, 5-fluorouracil, gemcitabine, or cytarabine.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Z79.631 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use for medications like methotrexate, 5-fluorouracil, gemcitabine, or cytarabine
- •Document alongside the primary malignancy code and monitor for bone marrow suppression