Billable / Specific Code
ICD-10-CM D89.40 is the diagnosis code for Mast cell activation, unspecified. This code falls under the section "Certain disorders involving the immune mechanism" within Chapter 3 — Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89). It is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. Medical coders and healthcare providers use this code to document and classify diagnoses in electronic health records, insurance claims, and clinical databases.
Understanding where D89.40 sits in the ICD-10-CM classification helps ensure proper coding:
Yes, D89.40 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
D89.40 is the ICD-10-CM diagnosis code for "Mast cell activation, unspecified". It is used by healthcare providers to classify and document this condition in medical records and insurance claims.
The parent code of D89.40 is D89.4 ("Mast cell activation syndrome and related disorders"). D89.40 provides a more specific classification within this category.
D89.40 is located in Section D80-D89 — "Certain disorders involving the immune mechanism" within Chapter 3 of the ICD-10-CM Tabular List.
Use D89.40 when the patients documented diagnosis matches "Mast cell activation, unspecified" and the clinical documentation supports this level of specificity. Always verify with the latest ICD-10-CM guidelines and payer requirements.
The ICD-10-CM code for Mast cell activation, unspecified is D89.40.
Yes, D89.40 can be used as a primary diagnosis code since it is billable and specific.
D89.40 is in Chapter 3 of the ICD-10-CM Tabular List.
Yes, D89.40 is a valid ICD-10-CM code for the 2026 fiscal year, subject to official CMS updates.