ICD-10 Code H70.0 – Acute mastoiditis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H70.0 – Acute mastoiditis
What it is
H70.0 identifies acute mastoiditis, an acute infection and inflammation of the mastoid air cells behind the ear. Use it when documentation clearly states mastoid involvement, often as a complication of ear infection.
Clinical signs
Typical findings include ear pain, fever, postauricular tenderness, swelling, or redness, and sometimes protrusion of the ear. Clinical features vary; refer to documentation.
When to use this code
Use H70.0 when the record documents acute mastoiditis or an acute mastoid infection. It may appear with otitis media or after persistent ear symptoms, but the provider must link the mastoid process to the acute condition. If the note is unclear, check documentation.
Do not use for
Do not use this code for chronic mastoiditis, nonspecific ear pain, or uncomplicated otitis media without mastoid involvement. Do not assume mastoiditis from imaging alone unless the provider documents the diagnosis.
Coding tip
Verify that the provider explicitly documents acute mastoiditis before assigning H70.0, and code any related ear infection only when separately supported.