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ICD-10-CM 2027 diagnosis code

H70.91Unspecified mastoiditis, right ear

✓ Billable / specific

H70.91 is a valid, billable ICD-10-CM code for unspecified mastoiditis, right ear. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

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 H70.91

H70.91 is the ICD-10-CM diagnosis code for unspecified mastoiditis, right ear. 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 billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within H70.9 (unspecified mastoiditis), H70.91 is specifically for unspecified mastoiditis, right ear. Related codes cover unspecified ear (H70.90), left ear (H70.92) and bilateral (H70.93).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 152 (Otitis Media and URI with MCC, relative weight 1.1151) and DRG 153 (Otitis Media and URI without MCC, relative weight 0.7421), in MDC 03 (Diseases and Disorders of the Ear, Nose, Mouth and Throat), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 383.9 (unspecified mastoiditis).

Notes that apply from higher levels

Instructions written at a parent level also apply to H70.91.

Broader instructions also apply from Chapter 8: Diseases of the ear and mastoid process.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 03 · Diseases and Disorders of the Ear, Nose, Mouth and Throat

ICD-9-CM equivalent

Converter →
  • 383.9Unspecified mastoiditisapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about H70.91

Is H70.91 billable?

Yes. H70.91 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can H70.91 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict H70.91 as a principal diagnosis.

Is H70.91 a CC or MCC?

No. H70.91 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does H70.91 group to?

H70.91 is used in the MS-DRG v44.0 logic for MS-DRG 152 (Otitis Media and URI with MCC) and MS-DRG 153 (Otitis Media and URI without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for H70.91?

The CMS General Equivalence Mappings map H70.91 to ICD-9-CM 383.9.