B35.1 Tinea unguium

The ICD-10-CM code for Tinea unguium is B35.1 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

1: Certain infectious and parasitic diseases (A00-B99)

Section

B35-B49: Mycoses (B35-B49)

Category B35

10 codes (9 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to B35.1:

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

Inclusion Terms

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

U.S. Hospital Utilization

• An estimated 44,670 U.S. inpatient stays in 2023 included B35.1 among the documented diagnoses.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

HIV Infections (TOC entry)

a. Human Immunodeficiency Virus (HIV) Infections .............................................................. 19

Infectious agents causing diseases in other chapters (TOC)

b. Infectious agents as the cause of diseases classified to other chapters ................................. 22

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)