ICD-10 Code for Mastoiditis

Also indexed as (coalescent) (hemorrhagic) (suppurative)

The ICD-10-CM code for mastoiditis is H70.9 — Unspecified mastoiditis. This is the code the Alphabetic Index gives for mastoiditis with no further qualifier, valid for FY2027 (October 1, 2026 – September 30, 2027).

Not billable

H70.9 cannot be submitted on a claim. It is a header code, so a more specific code from the list below is required.

Which mastoiditis code should you use?

The Alphabetic Index lists 10 codes under Mastoiditis. Which one applies depends on the qualifier documented in the record — the type, site, cause, or associated condition. Find the qualifier below, then verify the code in the Tabular List before using it.

By type

acute, subacute	H70.00Not billable	Acute mastoiditis without complications
chronic	H70.1Not billable	Chronic mastoiditis
specified NEC	H70.89Not billable	Other mastoiditis and related conditions
tuberculous	A18.03	Tuberculosis of other bones

Mastoiditis acute, subacute

complicated NEC	H70.09Not billable	Acute mastoiditis with other complications
subperiosteal	H70.01Not billable	Subperiosteal abscess of mastoid

Mastoiditis in

infectious disease NEC	B99Not billable	Other and unspecified infectious diseases
parasitic disease NEC	B89	Unspecified parasitic disease
tuberculosis	A18.03	Tuberculosis of other bones

Codes under H70.9

Index terms and codes are reproduced from the official ICD-10-CM FY2027 release. The Alphabetic Index is a finding aid — a code must always be verified in the Tabular List before it is reported. Data sources