Onychomycosis is a fungal nail infection. It affects the toenails or fingernails. The nails may turn dark, grow thicker, and start to crack.
In medical billing and diagnosis, the correct ICD-10 code is essential. Doctors use special codes to record these infections. It helps in medical records and billing.
In this guide, we’ll help you understand the ICD-10 code for onychomycosis, what it means, and how to use it accurately
Why Is Accurate Onychomycosis Coding Important?
Accurate coding helps:
- Get faster insurance approvals
- Prevent claim denials
- Support better treatment tracking
Common ICD-10 Codes Related to Onychomycosis
| Condition | ICD-10-CM code | Code description |
| Onychomycosis (fungal nail infection), fingernail or toenail | B35.1 | Tinea unguium |
B35.1 is the only code for onychomycosis. It covers both fingernails and toenails, and there is no separate code for side or digit. If the nail infection is caused by Candida rather than a dermatophyte, the code is B37.2 (candidiasis of skin and nail) instead.
Billing note for podiatry: treatment of mycotic nails is usually billed as nail debridement (CPT 11720 for one to five nails, 11721 for six or more). Medicare treats this as routine foot care unless the record shows a covered reason, such as pain, marked limitation of walking, or secondary infection, or qualifying systemic disease with class findings reported with modifiers Q7, Q8 or Q9. Check the local coverage determination for your Medicare contractor before billing.
What Causes Onychomycosis?
- Poor foot hygiene
- Walking barefoot in wet public areas
- Wearing tight shoes
- Having athlete’s foot
Symptoms of Nail Fungus
Look out for these signs:
- Yellow or white spots under the nail
- Thickened or brittle nails
- Nails that crumble or split
- Bad odor
How Is Onychomycosis Diagnosed?
Doctors usually examine the nails and may take a small sample. This sample is tested in a lab to confirm fungal infection. Once diagnosed, they use ICD-10 for onychomycosis for medical documentation.
Treatment Options for Onychomycosis
Treatment depends on the severity. Options include:
| Treatment | Description |
| Topical Creams | Applied directly to the nail |
| Oral Antifungals | Pills to kill the fungus from inside |
| Laser Therapy | Light-based treatment to target fungus |
| Nail Removal | In severe cases |
Related Skin Conditions and Their Codes
Fungal infections of other body sites have their own codes:
| Condition | ICD-10-CM code | Code description |
| Athlete’s foot | B35.3 | Tinea pedis |
| Jock itch | B35.6 | Tinea cruris |
| Ringworm of the body | B35.4 | Tinea corporis |
| Candida infection of skin or nail | B37.2 | Candidiasis of skin and nail |
| Nail dystrophy without confirmed fungus | L60.3 | Nail dystrophy |
How to Avoid Nail Fungus
Here are some prevention tips:
- Keep your feet clean and dry
- Don’t share nail tools
- Wear breathable socks
- Change socks regularly
Who is at Risk of Onychomycosis?
People with diabetes or weak immune systems are more prone. Risk increases with age. Athletes who use public showers or pools often are at higher risk too.
Coding Errors to Avoid
- Don’t use outdated codes
- Don’t mix up the jock itch code (B35.6) with nail fungus codes
- Make sure the fungus is confirmed before coding
Final Words
Using the right ICD code helps with diagnosis. It also helps with billing. B35.1 is the standard ICD-10 code for onychomycosis. You may also see it searched as the nail fungus ICD-10 code. They all point to the same issue.
Don’t ignore changes in your nails. Visit a provider. Early treatment makes recovery easier.
Prospect Healthcare Solutions is here to help. We provide accurate coding support. We work with clinics and doctors. Our goal is to make the coding process smooth and error-free.
At Prospect Healthcare Solutions, we care about your health. We support clinics and healthcare teams with expert ICD coding services.
FAQS
Q: Is B35.1 the ICD-10 code for both onychomycosis and nail fungus?
Yes. Onychomycosis is the medical term for a fungal nail infection, and both are coded B35.1 (tinea unguium).
Q: Can B35.1 be used for fungal infections on any nail, finger or toe?
Yes, the same code covers both.
Q:How many times should I report B35.1 on a claim?
Report B35.1 once on the claim and link it to each service it supports, such as nail debridement.
Q:What is the diagnosis (dx) code for onychomycosis?
“DX” means diagnosis. It is the code used by doctors.
Q:Are there other infections with similar ICD codes?
Yes. Jock itch (tinea cruris) is B35.6, athlete’s foot (tinea pedis) is B35.3, and a Candida nail infection is B37.2.
