Question 1

What is ICD-10 code H21.31?

Accepted Answer

H21.31 is the ICD-10-CM diagnosis code for Exudative cysts of iris or anterior chamber. It belongs to the ICD-10-CM chapter for diseases of the eye and adnexa (h00-h59). H21.31 is a non-billable header code that organizes more specific child codes; the actual diagnosis on a claim must use one of those children. H21.31 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Question 2

Is H21.31 an HCC code?

Accepted Answer

H21.31 is a non-billable header code, so it cannot itself be a payment HCC. Header codes organize more specific child codes that share the same root concept; one of those children may map to a payment HCC under the CMS-HCC V28 or V24 risk adjustment model. Coders should select a child code from the H21.31 hierarchy that matches the documented presentation, then check that specific child for HCC status.

Question 3

Is H21.31 billable?

Accepted Answer

No. H21.31 is a header (non-billable) ICD-10-CM code. Header codes sit at a higher level of the diagnosis hierarchy and exist to organize a family of more specific child codes. Per ICD-10-CM coding guidelines, a header code cannot be reported on a claim as the diagnosis, coders must select a billable child code from the H21.31 hierarchy that matches the highest level of specificity supported by the provider's documentation. Payers reject header codes submitted as the primary diagnosis.

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H21.31

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Child Codes

Code Hierarchy

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H21.31 ICD-10-CM Code: Exudative cysts of iris or anterior chamber