Medically reviewed by Dr. Tom Biernacki, DPM
Board-certified podiatric surgeon | Balance Foot & Ankle, Howell & Bloomfield Township, MI
Last reviewed: May 2026
Thick toenails are most often caused by fungus, repeated trauma, or psoriasis — and the right diagnosis is the difference between treatments that work in months and ones that do nothing for years.
You’re in the right place. Dr. Tom Biernacki, DPM, FACFAS — board-certified foot & ankle surgeon with 3,000+ surgeries — explains exactly what thick toenails causes means and what works. Call (810) 206-1402 for same-day appointment at Howell or Bloomfield Township.
Quick answer:Thick toenails are most often caused by fungal infection, past injury, or reduced circulation, and they become more common with age. A podiatrist can safely thin and treat them, identify the cause, and keep the thickening from getting worse. Call (810) 206-1402.
Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
Watch: Tea Tree Oil Toenail Fungus Home Treatment [Doctor Cure!] — MichiganFootDoctors YouTube
The most important clinical decision with Thick Toenails Causes isn’t which treatment to start with — it’s identifying the correct subtype. That changes everything. Call (810) 206-1402.
The most important clinical decision with Thick Toenails Causes isn’t which treatment to start with — it’s identifying the correct subtype. That changes everything. Call (810) 206-1402.
Why Do Toenails Get Thick?
Toenail thickening (onychauxis) occurs when the nail plate grows faster than it can shed, creating layers of keratinized nail material that accumulate over time. The nail plate is produced by the nail matrix — the living cells at the base of the nail — and any disruption to normal matrix function causes abnormal nail growth. Understanding the specific cause guides the correct treatment.
Onychomycosis (fungal nail infection): The leading cause of thick toenails, affecting 10% of the general population and up to 50% of adults over 70. Dermatophyte fungi (Trichophyton rubrum most commonly) invade the nail plate and nail bed, producing enzymes that destroy the nail keratin architecture and trigger hyperkeratotic thickening, discoloration, and fragility. Trauma: Repetitive microtrauma from shoe pressure (runner’s toe) or single acute trauma causes subungual hematoma and nail matrix disruption. The nail grows back thickened and distorted after significant trauma. Psoriasis: Nail psoriasis affects 80–90% of patients with psoriatic arthritis. Characteristic signs include pitting, oil-drop (salmon patch) discoloration, onycholysis (nail separation), and subungual hyperkeratosis (thick nail debris under the plate). Aging: Normal aging slows nail plate growth and produces a gradual thickening — particularly in older patients with reduced peripheral circulation.
Treatment Options
Professional debridement: Regardless of cause, mechanical reduction of the nail plate by a podiatrist removes the accumulated thickened nail, improves topical penetration, and immediately reduces discomfort from shoe pressure. This should be performed every 8–12 weeks for chronic thick nails. Oral antifungal: Terbinafine (Lamisil) 250mg daily for 12 weeks achieves mycological cure in 60–80% of onychomycosis cases. Lab confirmation (nail clipping culture or PAS stain) before treatment is recommended, as clinical appearance alone is not sufficient for diagnosis — only 50% of thick nails are actually fungal. Topical antifungal: Ciclopirox (Penlac) and efinaconazole (Jublia) have lower cure rates than oral therapy but are appropriate for mild disease or patients who cannot take oral terbinafine. Laser treatment: Nd:YAG laser safely delivers fungicidal energy through the nail plate. Effective for cases resistant to oral antifungal therapy or patients with medication contraindications.
Dr. Tom's Product Recommendations
Doctor Hoy’s Natural Pain Relief Gel
⭐ Highly Rated
For thick toenail patients with associated periungual (around the nail) inflammation and discomfort, Doctor Hoy’s arnica formula provides topical relief. Apply around (not under) the nail margins 1–2 times daily to reduce inflammation from shoe pressure on thickened nails.
Dr. Tom says: “For my thick nail patients waiting for antifungal treatment to work — which takes 9–12 months — Doctor Hoy’s around the nail margins reduces the periungual inflammation that causes daily shoe discomfort. It’s a practical comfort measure during the long treatment course.”
Periungual inflammation, shoe pressure discomfort with thick nails, temporary comfort
Do not apply under an onycholytic (separated) nail plate; active infection requires antifungal
Disclosure: We earn a commission at no extra cost to you.
✅ Pros / Benefits
- Oral terbinafine achieves 60–80% mycological cure rate
- Professional nail debridement provides immediate comfort relief
- Laser treatment effective for medication-resistant fungal infections
- Diagnosis with nail culture confirms fungal cause before initiating expensive oral treatment
❌ Cons / Risks
- Oral antifungal treatment takes 9–12 months to see full results
- Lab testing before treatment is under-used (50% of thick nails are not fungal)
- Recurrence after successful treatment is common without preventive measures
- Psoriatic nail disease cannot be treated with antifungals — requires dermatologic management
Dr. Tom Biernacki’s Recommendation
I culture every thick nail before prescribing oral terbinafine. Half of thick nails in my practice are not fungal — they’re traumatic, psoriatic, or aging-related. Treating a non-fungal thick nail with terbinafine is both ineffective and potentially hepatotoxic. The PAS stain nail clipping is a $30 test that prevents a lot of unnecessary treatment. Get the diagnosis right first.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
Are thick toenails always fungal?
No. Only about 50% of thick toenails have confirmed fungal infection. Trauma, psoriasis, aging, and poor circulation also cause nail thickening. A nail clipping for culture or PAS stain confirms the diagnosis.
How do I know if my thick toenails are fungal?
Clinical clues for fungal infection: yellowish-brownish discoloration, crumbling nail edges, white streaks (white superficial onychomycosis), and subungual debris. Confirmation requires laboratory testing (PAS stain or culture).
Can I file down thick toenails myself?
A nail file or emery board can thin mildly thickened nails for temporary comfort. Professional debridement by a podiatrist uses electric drills and proper instruments to safely reduce thick nails without damaging the nail bed.
How long does terbinafine take to clear nail fungus?
Terbinafine is taken for 12 weeks (fingernails) or 12–16 weeks (toenails). However, visible nail clearing takes 9–12 months as the new nail grows out from the matrix.
Does nail fungus spread to other toes?
Yes. Onychomycosis can spread from nail to nail and to the skin (athlete’s foot). Treating athlete’s foot simultaneously with nail fungus is essential to prevent re-infection.
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Dr. Tom Biernacki, DPM is a board-certified foot & ankle surgeon (ABFAS & ABPM) at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has made him one of the most-followed foot & ankle educators on YouTube.