ICD-10-CM 2027 diagnosis code
H70.1Chronic mastoiditis
H70.1 is a header code, so it can't be reported by itself. Choose one of the 4 more specific codes beneath it.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About H70.1
H70.1 is the ICD-10-CM diagnosis code for chronic mastoiditis. It belongs to category H70 (mastoiditis and related conditions), block H65-H75 (diseases of middle ear and mastoid) and chapter 8 (diseases of the ear and mastoid process). It is a header code, so it can't be reported by itself; one of its 4 subcodes must be used instead.
Within H70 (mastoiditis and related conditions), H70.1 is specifically for chronic mastoiditis. Related codes cover acute mastoiditis (H70.0), petrositis (H70.2), other mastoiditis and related conditions (H70.8) and unspecified mastoiditis (H70.9).
To report this condition, pick the subcode that matches the documentation: H70.10 (unspecified ear), H70.11 (right ear), H70.12 (left ear) and H70.13 (bilateral).
Don't report H70.1 together with the conditions in its Excludes1 note: tuberculous mastoiditis (A18.03).
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Specific codes under H70.1
Coding notes
- Caries of mastoid
- Fistula of mastoid
- tuberculous mastoiditis (A18.03)
Notes that apply from higher levels
Instructions written at a parent level also apply to H70.1.
Broader instructions also apply from Chapter 8: Diseases of the ear and mastoid process.
Alphabetic index entries
1 entriesTerms in the official ICD-10-CM index that lead to H70.1.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about H70.1
Is H70.1 billable?
- No. H70.1 is a header code. Report one of its more specific subcodes instead.