H20.1 ICD-10-CM Code: Chronic iridocyclitis

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for H20.1 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 H20.1

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

Before you code H20.1

1. H20.1 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).

   ReviewH20.10, H20.11, H20.12, H20.13

   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 H20.1?
   Yes → Select that code and continue the checks below on its own page.
   No → H20.1 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewH20.10, H20.11, H20.12, H20.13

Consider H20.1. Then work the Use Additional Code note, and 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).

Acuity

Acute or chronic as documented; when both are documented and separate codes exist, both are reported with the acute code first (Guidelines I.B.8).

The conditions the Use Additional Code note names

Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

Official instructions as workflow

• Excludes2 — not part of H20.1(1 note)

  Coding workflow: The conditions named in this note are not included in H20.1. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareH30.2

  See the official tabular notes · Guidelines I.A.12.b

• Use Additional Code — after identifying H20.1(1 note)

  Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with H20.1 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

  ReviewH26.21

  See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

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 H20.1 with…

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

The codes most likely to be picked instead of H20.1 — 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.

• H30.2— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of posterior cyclitis adds H30.2; it is not part of this code and both may be reported when both are documented.

  Full comparison: H20.1 vs H30.2 →

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: H20.10, H20.11, H20.12, H20.13.

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

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name H20.1 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Code Also instruction: H26.21 — Cataract with neovascularization.

These codes suggest coding this condition alongside when both are present.

Related Codes

Same Index main term, other category

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

A18.54 — Tuberculous iridocyclitis (tuberculous), A51.43 — Secondary syphilitic oculopathy (syphilitic), A54.32 — Gonococcal iridocyclitis (gonococcal), B00.51 — Herpesviral iridocyclitis (in, herpesvirus), B02.32 — Zoster iridocyclitis (in, zoster), B89 — Unspecified parasitic disease (in, parasitic disease NOS), B99 — Other and unspecified infectious diseases (in, infectious disease NOS), D86.83 — Sarcoid iridocyclitis (in, sarcoidosis), M45.9 — Ankylosing spondylitis of unspecified sites in spine (in, ankylosing spondylitis)

Contextual Map

Every relationship of H20.1 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.

Run H20.1 with these 2 related codes in Claim Check

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

Excludes2

• H30.2 — Posterior cyclitis[Excludes2]: “posterior cyclitis (H30.2-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Use Additional Code

• H26.21 — Cataract with neovascularization[Use Additional Code]: “code for any associated cataract (H26.21-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Code Also instructions

• H26.21 — Cataract with neovascularization[Code Also]: “chronic iridocyclitis (H20.1-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Nearest codes (40)

• H20 — Iridocyclitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.02 — Recurrent acute iridocyclitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.021 — Recurrent acute iridocyclitis, right eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.022 — Recurrent acute iridocyclitis, left eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.023 — Recurrent acute iridocyclitis, bilateral[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.029 — Recurrent acute iridocyclitis, unspecified eye[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.03 — Secondary infectious iridocyclitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H20.031 — Secondary infectious iridocyclitis, right 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 H20.1 in its code family, with their registry titles.

• H20.05 — Hypopyon
• H20.051 — Hypopyon, right eye
• H20.052 — Hypopyon, left eye
• H20.053 — Hypopyon, bilateral
• H20.059 — Hypopyon, unspecified eye
• H20.10 — Chronic iridocyclitis, unspecified eye
• H20.11 — Chronic iridocyclitis, right eye
• H20.12 — Chronic iridocyclitis, left eye
• H20.13 — Chronic iridocyclitis, bilateral
• H20.2 — Lens-induced iridocyclitis

View all codes in the H20 family