Z21 ICD-10-CM Code: Asymptomatic human immunodeficiency virus [HIV] infection status
HCC Buddy Code Card
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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 communicable diseases (Z20-Z29)
Z21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceAsymptomatic human immunodeficiency virus [HIV] infection status
A person who has tested positive for HIV but has not yet developed AIDS or shown symptoms of HIV infection.
Buddy Insight
Asymptomatic HIV infection status indicates ongoing viral infection requiring regular monitoring, antiretroviral therapy, and preventive care to prevent progression to AIDS.
CMS-HCC V28
MappedHCC 1
RAF 0.301
CMS-HCC V24
MappedHCC 1
RAF 0.335
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 1
RAF 0.0
RXHCC
MappedHCC 1
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
Official- HIV positive NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for Z21 in this effective period.
Related Child Codes
ICD-10-CM does not list child codes under Z21 for this display context.
Includes
OfficialICD-10-CM does not list Includes notes for Z21 in this effective period.
Excludes 1
Official- acquired immunodeficiency syndrome (B20)
- contact with human immunodeficiency virus [HIV] (Z20.6)
- exposure to human immunodeficiency virus [HIV] (Z20.6)
- human immunodeficiency virus [HIV] disease (B20)
- inconclusive laboratory evidence of human immunodeficiency virus [HIV] (R75)
Code First
Official- Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable (O98.7-)
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for Z21 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for Z21 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is Z21 an HCC code?
Yes. Z21 maps to HIV/AIDS under the CMS-HCC V28 risk adjustment model (and HIV/AIDS under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
Work Z21 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for Z21
For Z21to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed Z21 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
Z21 is the ICD-10-CM diagnosis code for asymptomatic human immunodeficiency virus [hiv] infection status. A person who has tested positive for HIV but has not yet developed AIDS or shown symptoms of HIV infection. Z21 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 communicable diseases (z20-z29).
Under the CMS-HCC V28 risk adjustment model, Z21 maps to HIV/AIDS (HCC 1) with a community, non-dual, aged base RAF weight of 0.301. Under the older V24 model, Z21 mapped to the same category but with a base RAF weight of 0.335, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This code indicates asymptomatic HIV status; if the patient develops AIDS or symptomatic disease, use B20 codes instead. Because Z21 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Z21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code indicates asymptomatic HIV status; if the patient develops AIDS or symptomatic disease, use B20 codes instead
- •Document the patient's CD4 count and viral load status in the medical record for comprehensive care tracking
Clinical Significance
Asymptomatic HIV infection status indicates ongoing viral infection requiring regular monitoring, antiretroviral therapy, and preventive care to prevent progression to AIDS. This diagnosis represents a chronic condition with significant implications for immune system function and overall health management.
Documentation Requirements
- ✓Laboratory confirmation of HIV-positive status
- ✓Documentation that patient is asymptomatic for HIV disease
- ✓Current CD4 count and viral load results when available
- ✓Antiretroviral therapy regimen if prescribed
- ✓Assessment of HIV disease stage or classification
- ✓Screening for opportunistic infections
- ✓Counseling and education provided
- ✓Plans for ongoing HIV monitoring and care
Excludes 1, Do NOT code together
Code First
- Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable (O98.7-)
Commonly Confused Codes
- •B20: Human immunodeficiency virus disease (symptomatic HIV/AIDS)
- •Z87.891: Personal history of nicotine dependence (different risk factor)
- •Z11.4: Encounter for screening for human immunodeficiency virus
- •R75: Inconclusive laboratory evidence of human immunodeficiency virus
- •O98.72: Human immunodeficiency virus disease complicating pregnancy