Is Z21 a billable ICD-10-CM code?

Yes. Z21 is a billable, specific ICD-10-CM code and is valid for submission on a claim.

Where does Z21 sit in the tabular list?

Factors influencing health status and contact with health services (Z00-Z99), in the block Persons with potential health hazards related to communicable diseases (Z20-Z29).

What cannot be coded together with Z21?

Z21 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

Z21

Z21 — Asymptomatic human immunodeficiency virus [HIV] infection status

Billable / specific codeICD-10-CM

Z21 is a billable, specific ICD-10-CM code for asymptomatic human immunodeficiency virus [hiv] infection status. It is valid for submission on a claim.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

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

The underlying condition must be sequenced before this code.

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

Inclusion terms

Alternative wordings a physician may use in the chart for this same code.

HIV positive NOS

Other codes that can never be billed with Z21

These codes carry an Excludes1 note pointing at Z21. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading Z21 alone.

B20Human immunodeficiency virus [HIV] disease
R75Inconclusive laboratory evidence of human immunodeficiency virus [HIV]
Z20.6Contact with and (suspected) exposure to human immunodeficiency virus [HIV]

Risk adjustment

Z21 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:

HCC 1 HIV/AIDS0.301 RAF

Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.

Medicare coverage

Z21 is named in 10 Medicare coverage policies — 10 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

A55717Billing and Coding: Lab: Flow Cytometry
A56464Billing and Coding: Flow Cytometry
A57689Billing and Coding: Lab: Flow Cytometry
A58710Billing and Coding: MolDX: Molecular Syndromic Panels for Infectious Disease Pathogen Identification Testing

How Z21 is indexed

Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to Z21.

HIV›positive, seropositive
Status›human immunodeficiency virus infection, asymptomatic(HIV)
Syndrome›retroviral seroconversion(acute)
Syndrome›seroconversion, retroviral(acute)
Human›immunodeficiency virus›asymptomatic status
Test, tests, testing›HIV›positive
Test, tests, testing›HIV›seropositive

Questions about Z21

Is Z21 a billable ICD-10-CM code?: Yes. Z21 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does Z21 sit in the tabular list?: Factors influencing health status and contact with health services (Z00-Z99), in the block Persons with potential health hazards related to communicable diseases (Z20-Z29).
What cannot be coded together with Z21?: Z21 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.