2027 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 2027 (October 1, 2026 through September 30, 2027) 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 2027.
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 2027.
Source: CMS Payment Year 2027 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
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to Z21: its own notes plus those printed at Chapter 21. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- HIV positive NOS
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Code First
The underlying condition named in the note is sequenced before this code.
- Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable (O98.7-)
Notes
General instructions on how these codes are used.
- Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
- (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
- (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name Z21, its category, or a range that includes it.
Excludes1 3
These codes carry an Excludes1 note naming Z21: they are not reported together with it, unless the two conditions are unrelated.
- B20 Human immunodeficiency virus [HIV] diseaseasymptomatic human immunodeficiency virus [HIV] infection status (Z21)
- R75 Inconclusive laboratory evidence of human immunodeficiency virus [HIV]asymptomatic human immunodeficiency virus [HIV] infection status (Z21)
- Z20.6 Contact with and (suspected) exposure to human immunodeficiency virus [HIV]HIV infection status (Z21)
Excludes2 2
These codes carry an Excludes2 note naming Z21: its condition is not part of those codes, and both may be reported when the patient has both.
- Block P35-P39 Infections specific to the perinatal periodasymptomatic human immunodeficiency virus [HIV] infection status (Z21)
- Z78 Other specified health statusasymptomatic human immunodeficiency virus [HIV] infection status (Z21)
Use Additional Code 2
These codes say to use an additional code from the note, and Z21 is one of the codes named.
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, 2026 through September 30, 2027.
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, 2026 through September 30, 2027.
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 866, 865, with relative weights from 0.8691 to 1.3153 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.
Can Z21 be reported with B20?
Not as a rule. The Excludes1 note on Z21 lists "acquired immunodeficiency syndrome (B20)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
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 2027. 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.
