Skip to main content
Call AIBook a demo

ICD-10-CM Z21: Asymptomatic human immunodeficiency virus [HIV] infection status

Z21 is the billable ICD-10-CM code for asymptomatic human immunodeficiency virus [HIV] infection status, in category Z21 (Asymptomatic human immunodeficiency virus [HIV] infection status) of the Persons with potential health hazards related to communicable diseases section. As a principal diagnosis it groups to MS-DRG 865 Viral Illness with MCC, MS-DRG 866 Viral Illness without MCC (MDC 18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites). It maps to HCC 1 (HIV/AIDS) in CMS-HCC V28. 10 LCD billing and coding articles list it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
Z21
billable FY2027 ICD-10-CM code
Category
Z21 Asymptomatic human immunodeficiency virus [HIV] infection status
Chapter
21: Factors influencing health status and contact with health services (Z00-Z99)
CC/MCC (MS-DRG v44)
Neither
CMS-HCC V28
HCC 1
POA reporting
Required

Tabular list notes for Z21

Inclusion terms
  • HIV positive NOS
Excludes1 (never coded together)
  • 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
  • Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable (O98.7-)

MS-DRG grouping when Z21 is the principal diagnosis

MS-DRG v44 groups for Z21 as principal diagnosis
MDCMS-DRGs
18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites865866

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for Z21 shows the full grouping logic.

CC/MCC status and inpatient edits

Z21 is neither a CC nor an MCC under MS-DRG v44, so as a secondary diagnosis it does not raise the MS-DRG severity level. Check Z21 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.
  • Medicare Code Editor: questionable admission as principal diagnosis.

CMS-HCC V28 risk adjustment

In the PY2027 mapping, Z21 maps to HCC 1 (HIV/AIDS). The HCC lookup shows the RAF weight and the hierarchy.

LCD billing and coding articles that list Z21

10 current Medicare billing and coding articles list Z21 among the diagnoses that support medical necessity for the services they cover.

For teams evaluating QuickIntell software

Evaluate software for diagnosis coding review

If your team codes diagnoses at volume, review how QuickCode supports qualified coder review of documentation, specificity queries and the billing handoff. Confirm the code sets, settings and reviewer responsibilities during evaluation; a code reference is not a coding determination for a patient.

Evaluate QuickCode for diagnosis codingSee risk adjustment review
Book a software demoAsk about a software workflow

Optional software evaluation, not payer support or help with an individual claim. For coverage or payment decisions, use the official sources on this page. Do not include patient information in a demo booking or inquiry.

Frequently asked questions

What does ICD-10-CM Z21 mean?

Z21 means asymptomatic human immunodeficiency virus [HIV] infection status. The tabular list also files these terms under it: HIV positive NOS. It is one of 1 billable codes under Z21, asymptomatic human immunodeficiency virus [HIV] infection status.

What can't be coded with Z21?

Excludes1 at Z21: 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) and 1 more. These are never reported together with Z21.

What else is coded with Z21?

The tabular instructions at Z21: Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable (O98.7-).

Which MS-DRG does Z21 group to?

As the principal diagnosis, Z21 groups to MS-DRG 865 Viral Illness with MCC, MS-DRG 866 Viral Illness without MCC (MDC 18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Does Z21 map to an HCC?

Yes: HCC 1, HIV/AIDS, in the PY2027 CMS-HCC V28 mapping.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.