H16.32 ICD-10-CM Code: Diffuse interstitial keratitis

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for H16.32 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Coder workflow for H16.32

MedCoder structured workflow — derived from this code’s own official record

Before you code H16.32

1. H16.32 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

   ReviewH16.321, H16.322, H16.323, H16.329

   See the relationships section · Guide: How to choose an ICD-10-CM code →

Choose the right path

1. Does the documentation support one of the more specific codes beneath H16.32?
   Yes → Select that code and continue the checks below on its own page.
   No → H16.32 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewH16.321, H16.322, H16.323, H16.329

Consider H16.32. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse H16.32 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of H16.32 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• H16.30— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “Unspecified interstitial keratitis” takes H16.30; specificity in the record moves it back here.

  Full comparison: H16.32 vs H16.30 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• Not billable as written — a more specific code is required: H16.321, H16.322, H16.323, H16.329.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Related Codes

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Cogan's syndrome”, “Keratitis”; these codes share that main term but sit in a different category of the Tabular List.

A18.52 — Tuberculous keratitis (tuberculous), A30.9 — Leprosy, unspecified (punctata, leprosa), A50.31 — Late congenital syphilitic interstitial keratitis (syphilitic), A54.33 — Gonococcal keratitis (gonococcal), A71.1 — Active stage of trachoma (trachomatous), B00.52 — Herpesviral keratitis (disciform), B01.81 — Varicella keratitis (disciform, varicella), B02.33 — Zoster keratitis (in, zoster), B05.81 — Measles keratitis and keratoconjunctivitis (in, measles), B09 — Unspecified viral infection characterized by skin and mucous membrane lesions (in, exanthema), B30.0 — Keratoconjunctivitis due to adenovirus (in, adenovirus), B60.13 — Keratoconjunctivitis due to Acanthamoeba (in, acanthamebiasis), B94.0 — Sequelae of trachoma (trachomatous, sequelae), E50.4 — Vitamin A deficiency with keratomalacia (xerotic, vitamin A deficiency), H51.8 — Other specified disorders of binocular movement (oculomotor apraxia), L71.8 — Other rosacea (rosacea)

Contextual Map

Every relationship of H16.32 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

• H00-H59 — Chapter 7: Diseases of the Eye and Adnexa (H00-H59) (H00-H59)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H15-H22 — Disorders of sclera, cornea, iris and ciliary body[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Nearest codes (40)

• H16 — Keratitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.261 — Vernal keratoconjunctivitis, with limbar and corneal involvement, right eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.262 — Vernal keratoconjunctivitis, with limbar and corneal involvement, left eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.263 — Vernal keratoconjunctivitis, with limbar and corneal involvement, bilateral[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.269 — Vernal keratoconjunctivitis, with limbar and corneal involvement, unspecified eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.29 — Other keratoconjunctivitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.291 — Other keratoconjunctivitis, right eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H16.292 — Other keratoconjunctivitis, left eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Common coding questions

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to H16.32 in its code family, with their registry titles.

• H16.31 — Corneal abscess
• H16.311 — Corneal abscess, right eye
• H16.312 — Corneal abscess, left eye
• H16.313 — Corneal abscess, bilateral
• H16.319 — Corneal abscess, unspecified eye
• H16.321 — Diffuse interstitial keratitis, right eye
• H16.322 — Diffuse interstitial keratitis, left eye
• H16.323 — Diffuse interstitial keratitis, bilateral
• H16.329 — Diffuse interstitial keratitis, unspecified eye
• H16.33 — Sclerosing keratitis

View all codes in the H16 family