ICD-10 Code D81.9 – Combined Immunodeficiency, Unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D81.9 – Combined immunodeficiency, unspecified
What it is
D81.9 identifies an unspecified combined immunodeficiency, meaning the patient has a serious defect affecting both cellular and humoral immune function, but the type is not further defined in the record.
Clinical signs
Clinical features vary; refer to documentation. Commonly, patients have recurrent or severe infections, poor response to routine infections, and signs suggesting broader immune dysfunction.
When to use this code
Use D81.9 when the provider documents combined immunodeficiency but does not name a specific subtype. It also fits when the chart confirms immune deficiency involving both arms of immunity, yet details are incomplete. Code this only from provider documentation, not from suspicion alone.
Do not use for
Do not use this code for isolated antibody deficiency, neutropenia, or other single-system immune disorders. If the record names a specific combined immunodeficiency, code that condition instead.
Coding tip
Check the note for a named subtype or a more specific immune disorder before defaulting to D81.9.