Z21 ICD-10-CM Code: Asymptomatic human immunodeficiency virus [HIV] infection status
Z21 maps to CMS-HCC V28 1. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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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
Coefficient HCC 1: 0.301 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 001
Code-level coefficient reference
ESRD/PACE
MappedHCC 1
Code-level coefficient reference
RXHCC
MappedHCC 1
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- HIV positive NOS
Excludes 2
OfficialNo Excludes 2 notes are included in this display for Z21. Check the code and parent instructions in the Code Book.
Related Codes
No related codes are included in this display for Z21. Check the Code Book for the complete code path.
Includes
OfficialNo Includes notes are included in this display for Z21. Check the code and parent instructions in the Code Book.
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
OfficialNo Use Additional Code instructions are included in this display for Z21. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for Z21. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 Z21 an HCC code?
Yes. Z21 (Asymptomatic human immunodeficiency virus [HIV] infection status) maps to HCC 1, HIV/AIDS under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.301. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: Z21 is billable and maps to V28 HCC 1, HIV/AIDS. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- Z21
- Description
- Asymptomatic human immunodeficiency virus [HIV] infection status
- HCC (V28)
- HCC 1 — HIV/AIDS
- RAF reference coefficient
- 0.301
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work Z21 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for Z21
For Z21, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
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 source-labeled community, non-dual, aged reference coefficient of 0.301. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Asymptomatic HIV infection status, HIV-positive without clinical manifestations or AIDS-defining conditions. Used for patients who have never had HIV disease (B20 criteria). For Z21, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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
- •Asymptomatic HIV infection status, HIV-positive without clinical manifestations or AIDS-defining conditions. Used for patients who have never had HIV disease (B20 criteria).
- •Once a patient meets B20 criteria, do not revert to Z21 even if currently asymptomatic on therapy, the B20 diagnosis is durable per ICD-10-CM rules.
- •Both symptomatic HIV disease (B20) and asymptomatic HIV status (Z21) capture HCC 1, so do not treat Z21 as a non-risk-adjusting status code.
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