Is ICD-10-CM code Z21 billable?

Yes, Z21 (Asymptomatic human immunodeficiency virus [HIV] infection status) is a billable ICD-10-CM diagnosis code, valid for reimbursement on HIPAA-covered transactions for FY2027.

What chapter does ICD-10-CM code Z21 belong to?

Z21 belongs to Chapter 21 of the ICD-10-CM tabular list: Z00–Z99 (Factors Influencing Health Status and Contact with Health Services).

Z21Billable, valid for claims from October 1, 2026

Asymptomatic human immunodeficiency virus [HIV] infection status

In Persons with potential health hazards related to communicable diseases (Z20-Z29), chapter 21: Factors Influencing Health Status and Contact with Health Services

Z21 is billable and valid on claims for FY 2027. If the record has more detail, check the other codes under Z20-Z29 below.
As a secondary diagnosis it is not a CC or MCC, so it doesn't raise the MS-DRG payment.
Counts toward HCC 1 (HIV/AIDS) in the Medicare Advantage risk model (CMS-HCC V28).
Medicare questions an inpatient admission when this is the principal diagnosis. (Questionable Admission list)

Also indexed as: HIV, positive, seropositive; Human, immunodeficiency virus disease, asymptomatic status; Status, human immunodeficiency virus infection, asymptomatic; Syndrome, retroviral seroconversion; Syndrome, seroconversion, retroviral; Test, HIV, positive; Test, HIV, seropositive

Instructional notes

Includes: conditions that are coded here

HIV positive NOS

Excludes1: not coded here, use a different code

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: code the underlying condition first, then this code

Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium, if applicable (O98.7-)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Section I.C.1.a Human Immunodeficiency Virus (HIV) Infections (page 19), covers Z21
Code only confirmed HIV, where the provider's statement is enough. Assign B20 for AIDS or any HIV-related illness, Z21 for asymptomatic HIV positive status, and R75 for inconclusive serology. Once B20 applies, use it on every later encounter.

Other codes under Z20-Z29

Persons with potential health hazards related to communicable diseases (Z20-Z29)

Z20Contact with and (suspected) exposure to communicable diseases
Z21Asymptomatic human immunodeficiency virus [HIV] infection status(this code)
Z22Carrier of infectious disease
Z23Encounter for immunization
Z28Immunization not carried out and underimmunization status
Z29Encounter for other prophylactic measures

Z21 MS-DRGs

As the principal diagnosis, Z21 groups to MS-DRG 865 or 866 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

Related conditions

Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.

Z21 is in HIV infection (INF006, its default category), with 10 codes. Others in it:

B20 Human immunodeficiency virus [HIV] disease
B97.35 Human immunodeficiency virus, type 2 [HIV 2] as the cause of diseases classified elsewhere
E88.14 HIV-associated lipodystrophy
O98.711 Human immunodeficiency virus [HIV] disease complicating pregnancy, first trimester
O98.712 Human immunodeficiency virus [HIV] disease complicating pregnancy, second trimester
O98.713 Human immunodeficiency virus [HIV] disease complicating pregnancy, third trimester
O98.719 Human immunodeficiency virus [HIV] disease complicating pregnancy, unspecified trimester
O98.72 Human immunodeficiency virus [HIV] disease complicating childbirth

Medicare coverage articles listing Z21

These 5 Medicare billing and coding articles list Z21 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.

MolDX: Molecular Syndromic Panels for Infectious Disease Pathogen Identification Testing (4 contractors)
Lab: Flow Cytometry (2 contractors)
Pharmacogenomics Testing (2 contractors)
Flow Cytometry
Pharmacogenomic Testing

Other codes that refer to Z21

Notes on these codes point to Z21.

B20 Excludes1: asymptomatic human immunodeficiency virus [HIV] infection status (Z21)
O98.7 Use Additional Code: Asymptomatic HIV status (Z21)
O98.7 Use Additional Code: HIV positive NOS (Z21)
P35-P39 Excludes2: asymptomatic human immunodeficiency virus [HIV] infection status (Z21)
R75 Excludes1: asymptomatic human immunodeficiency virus [HIV] infection status (Z21)
Z20.6 Excludes1: HIV infection status (Z21)
Z78 Excludes2: asymptomatic human immunodeficiency virus [HIV] infection status (Z21)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

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.

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.

ICD-9-CM equivalent

Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).

V08 Asymptomatic human immunodeficiency virus [HIV] infection status

ICD-9 to ICD-10 converter