2026 ICD-10-CM Diagnosis Code B35.1Tinea unguium

ICD-10-CM Codes›A00–B99›B35-B49›B35

ICD-10-CM B35.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B35.1 is a billable ICD-10-CM diagnosis code for tinea unguium. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 606 through 607. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fungal infections.

Code Identity

ICD-10-CM Code
B35.1
Billable Status
Yes — Valid for Submission
Code Describes
Tinea unguium
Short Description
Tinea unguium
Same as the full description in the CMS dataset.
Parent Code
B35
Dermatophytosis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB35-B49Mycoses
CategoryB35Dermatophytosis
This CodeB35.1Tinea unguium

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Distal and lateral subungual onychomycosis
  • Endonyx onychomycosis
  • Fusarium infection
  • Infection caused by Scytalidium
  • Infection of skin caused by Neoscytalidium dimidiatum
  • Infection of toenail
  • Nail bed infection
  • Neoscytalidium dermatomycosis
  • Onycholysis
  • Onycholysis due to fungal infection of nail
  • Onychomycosis
  • Onychomycosis caused by Acremonium
  • Onychomycosis caused by Botryodiplodia theobromae
  • Onychomycosis caused by Curvularia lunata
  • Onychomycosis caused by Epidermophyton floccosum
  • Onychomycosis caused by Fusarium
  • Onychomycosis caused by mold
  • Onychomycosis caused by Neocucurbitaria unguis-hominis
  • Onychomycosis caused by Neoscytalidium dimidiatum
  • Onychomycosis caused by Onychocola canadensis
  • Onychomycosis caused by Pseudeurotium ovale
  • Onychomycosis caused by Scopulariopsis brevicaulis
  • Onychomycosis caused by Scytalidium hyalinum
  • Onychomycosis caused by Trichophyton mentagrophytes
  • Onychomycosis caused by Trichophyton mentagrophytes variant interdigitale
  • Onychomycosis caused by Trichophyton rubrum
  • Onychomycosis caused by Trichophyton schoenleinii
  • Onychomycosis caused by Trichophyton soudanense
  • Onychomycosis caused by Trichophyton tonsurans variant tonsurans
  • Onychomycosis caused by Trichophyton violaceum
  • Onychomycosis due to dermatophyte
  • Onychomycosis due to opportunistic infection
  • Onychomycosis of nail of digit
  • Onychomycosis of toenails
  • Proximal subungual onychomycosis
  • Scytalidium hyalinum infection of skin
  • Superficial white onychomycosis
  • Tinea caused by Epidermophyton floccosum
  • Tinea caused by Trichophyton mentagrophytes variant interdigitale
  • Tinea caused by Trichophyton rubrum
  • Tinea caused by Trichophyton soudanense
  • Tinea caused by Trichophyton tonsurans
  • Tinea caused by Trichophyton violaceum
  • Total dystrophic onychomycosis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Dermatophytic onychia
  • Dermatophytosis of nail
  • Onychomycosis
  • Ringworm of nails

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Dermatophytosis(epidermophyton) (infection) (Microsporum) (tinea) (Trichophyton)
      • nail
    • Infection, infected, infective(opportunistic)
      • finger (skin)
        • nail
          • fungus
    • Infection, infected, infective(opportunistic)
      • fungus NOS
        • nail
    • Infection, infected, infective(opportunistic)
      • fungus NOS
        • skin
          • toenails
    • Infection, infected, infective(opportunistic)
      • nail (chronic)
        • finger
          • fungus
    • Infection, infected, infective(opportunistic)
      • nail (chronic)
        • toe
          • fungus
    • Infection, infected, infective(opportunistic)
      • toe (skin)
        • cellulitis
          • fungus
    • Infection, infected, infective(opportunistic)
      • toe (skin)
        • nail
          • fungus
    • Mycosis, mycotic
      • nails
    • Onychia
      • dermatophytic
    • Onychomycosis(finger) (toe)
    • Ringworm
      • nails
    • Tinea(intersecta) (tarsi)
      • unguium

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF004
Fungal infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Onychomycosis

    a fungal infection of the nail, usually caused by dermatophytes; yeasts; or nondermatophyte molds.

  • Onycholysis

    separation of nail plate from the underlying nail bed. it can be a sign of skin disease, infection (such as onychomycosis) or tissue injury.

  • Onycholysis

    a nail condition characterized by spontaneous separation of a fingernail or toenail from its nail bed.

  • Nail Loss, PRO-CTCAE|Nail loss|Onycholysis, PRO-CTCAE|PRO-CTCAE, Nail Loss

    onycholysis as recorded on the pro-ctcae questionnaire.

Patient EducationClinical

Tinea Infections

Tinea is the name of a group of diseases caused by a fungus. Types of tinea include ringworm, athlete's foot and jock itch. These infections are usually not serious, but they can be uncomfortable. You can get them by touching an infected person, from damp surfaces such as shower floors, or even from a pet.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert B35.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
110.1 Dermatophytosis of nail
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About B35.1Overview

Is B35.1 (Dermatophytosis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report tinea unguium on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does B35.1 group to?

When tinea unguium is the principal diagnosis on an inpatient stay, it groups to MS-DRG 606, 607, with relative weights from 0.9064 to 1.5132 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of B35.1?

Under the General Equivalence Mappings, tinea unguium converts to ICD-9-CM 110.1 (dermatophytosis of nail). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.