2026 ICD-10-CM Diagnosis Code Z21Asymptomatic human immunodeficiency virus [HIV] infection status
Z21 is a billable ICD-10-CM diagnosis code for asymptomatic human immunodeficiency virus [HIV] infection status. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 865 through 866. The code is flagged as a questionable admission, since it rarely justifies inpatient admission on its own. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under HIV infection.
For Medicare Advantage risk adjustment, Z21 maps to CMS-HCC Category 1 (HIV/AIDS) under the V28 model, adding a risk factor of about 0.301 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for Z21.
Medicare Risk Adjustment (HCC)Billing
Z21 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Analyte not reportable due to high human immunodeficiency virus antibody
- Asymptomatic human immunodeficiency virus A1 infection
- Asymptomatic human immunodeficiency virus A2 infection
- Asymptomatic human immunodeficiency virus infection
- Asymptomatic human immunodeficiency virus infection in pregnancy
- History of asymptomatic human immunodeficiency virus infection
- HIV CDC stage finding
- HIV detected
- Human immunodeficiency virus 2 antibody detected and Human immunodeficiency virus 1 antibody cross-reactivity
- Human immunodeficiency virus antibody detected
- Human immunodeficiency virus carrier
- Human immunodeficiency virus Centers for Disease Control and Prevention stage 0
- Human immunodeficiency virus complicating pregnancy childbirth and the puerperium
- Human immunodeficiency virus enzyme-linked immunosorbent assay test positive
- Human immunodeficiency virus I infection
- Human immunodeficiency virus II infection
- Increased human immunodeficiency virus viral load
- Viral load increased
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- HIV positive NOS
Code First
- Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable O98.7
Type 1 Excludes
- 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
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Status (post) See Also: Presence (of);
Syndrome See Also: Disease;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
HIV
HIV stands for human immunodeficiency virus. HIV harms your immune system by destroying a type of white blood cell that helps your body fight infection. This puts you at risk for other infections and diseases.
The full article covers:
- What is HIV?
- What is AIDS?
- How does HIV spread?
- Who is at risk for HIV infection?
- What are the symptoms of HIV?
- How do I know if I have HIV?
- What are the treatments for HIV?
- Can HIV infection be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert Z21 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About Z21Overview
What is the ICD-10 code for asymptomatic human immunodeficiency virus [HIV] infection status?
The ICD-10-CM code for asymptomatic human immunodeficiency virus [HIV] infection status is Z21. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is Z21 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report asymptomatic human immunodeficiency virus [HIV] infection status on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does Z21 group to?
When asymptomatic human immunodeficiency virus [HIV] infection status is the principal diagnosis on an inpatient stay, it groups to MS-DRG 865, 866, with relative weights from 0.8696 to 1.4983 depending on complications. Higher weights mean higher Medicare reimbursement.
Does Z21 justify an inpatient admission?
Not on its own. The Medicare Code Editor lists this code as a questionable admission because asymptomatic human immunodeficiency virus [HIV] infection status is not usually sufficient justification for admission to an acute care hospital.
What is the ICD-9 equivalent of Z21?
Under the General Equivalence Mappings, asymptomatic human immunodeficiency virus [HIV] infection status converts to ICD-9-CM V08 (asymp hiv infectn status). The mapping is a direct match.
What HCC is Z21?
Z21 (asymptomatic human immunodeficiency virus [HIV] infection status) maps to CMS-HCC Category 1 (HIV/AIDS), commonly written as HCC 1, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 1 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 1.
Does Z21 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, Z21 adds a risk adjustment factor of about 0.301 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.109 to 1.322 depending on the payment segment). HCC 1 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 1 category page.
