HIV Coding Changes for FY 2026: What Coders Need to Know

Overview of FY 2026 ICD-10-CM Coding Guideline Updates

With CMS’s push towards greater clinical granularity and documentation specificity, the FY 2026 ICD-10-CM Coding Guidelines, which go into effect October 1, 2025, introduces over 487 new diagnosis codes, revises 38, and deletes 28 codes. This is nearly doubling the volume of new codes over FY 2025. 

Changes to HIV Coding Guidelines in Section I.C.1.a.2

One of those major changes involves how coders select and sequence human immunodeficiency virus (HIV) codes. These changes to the guidelines, in section I.C.1.a.2, include various scenarios involving patients before, during, and after an HIV diagnosis. 

• I.C.1.a.2(a) tells you to assign B20 Human immunodeficiency virus [HIV] disease when physician documentation indicates the patient has acquired immunodeficiency syndrome (AIDS), HIV, “or if the patient is treated for any HIV-related illness or is described as having any condition(s) resulting from the patient’s HIV positive status.” 

• I.C.1.a.2(c) adds clarification that you can assign B20 as a secondary diagnosis for patients with HIV who have been admitted “for an unrelated condition (such as a traumatic injury).” Per the guideline revision, the same is now going to be true for “other documented conditions.” 

• I.C.1.a.2(e) clarifies use of Z21 Asymptomatic human immunodeficiency virus [HIV] infection status. You are told to apply the code when, “‘HIV positive,’ ‘HIV test positive,’ or similar terminology is documented, and there is no documentation of symptoms or HIV-related illness.” 

• I.C.1.a.2(f) still tells you to assign R75 Inconclusive laboratory evidence of human immunodeficiency virus [HIV] for patients with inconclusive serology of HIV; however, the language “but no definitive diagnosis or manifestations of the illness” has been deleted. Patients previously diagnosed with HIV continue to assign B20, but now the diagnosis will have to be documented and not “previously known,” per guideline revision. 

• I.C.1.a.2(h) tells you to assign O98.7 Human immunodeficiency virus [HIV] disease complicating pregnancy, childbirth and the puerperium only “when a patient presents during pregnancy, childbirth or the puerperium with documented symptomatic HIV disease or an HIV related illness.” Also assign Z21 for pregnant patients, patients giving birth, and for patients during the puerperium who are either HIV-positive or who have documented asymptomatic HIV. 

• I.C.1.a.2(i), the language changes from “If a patient is being seen to determine his/her HIV status,” to “If a patient without signs or symptoms is tested for HIV.” Additionally, for patients with signs and symptoms presenting for testing, you are now told not to report Z11.4 Encounter for screening for human immunodeficiency virus [HIV]. 



• I.C.1.a.2(j) provides revised instructions for reporting HIV-positive patients who are being treated with an antiretroviral medication. In FY 2026, assign Z21 “in the absence of any additional documentation of HIV disease, HIV-related illness or AIDS.” 
  

Practical Documentation and Coding Considerations

• Documentation specificity is critical 
• Look for exact terms (“HIV positive,” “AIDS,” “HIV disease,” “asymptomatic HIV”). Query if unclear. 
• Sequence by admission reason   
• HIV-related = B20 as principal. 
• Unrelated dx = that condition is principal and B20 secondary. 
• Never revert from B20 
• Once HIV-related illness is documented, always use B20 on future encounters. 
• Apply pregnancy rules  
• Use O98.7 first, then B20 or Z21 based on symptoms/illness. 
• Add management/prevention codes 
• Use Z79.899 for antiretrovirals 
• Z29.81 for PrEP (pre-exposure prophylaxis); any risk factors should also be coded.