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Yeast, Nail — Qualitative, KOH Preparation

Published: August 9, 2026Updated: August 17, 2026

A microscopic examination of nail material for yeast, commonly used to help evaluate a suspected fungal nail infection.

Quick summary

["A positive result means yeast was observed in the nail sample and may support a diagnosis of fungal nail infection."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
55314-9
Short code
Yeast Nail Ql KOH Prep
Synonyms
Yeast Nail Ql KOH Prep
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
koh-preparation
CPT
84484
SNOMED
302774002
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test examines a sample of nail material for yeast. The sample is treated with potassium hydroxide (KOH) and viewed under a microscope to look for fungal cells.

Why might I need this test?

It may be ordered when a nail is thickened, discolored, crumbly, or otherwise appears infected. The result can help determine whether yeast is a possible cause of the nail changes.

How is the test performed?

A clinician collects small amounts of material from the affected nail. The laboratory prepares it with KOH and examines it microscopically, reporting whether yeast is present.

How do I prepare for the test?

Follow any instructions from your clinician about which nail or area to have sampled. Before the visit, avoid painting the affected nails and do not trim or remove the material that will be collected unless instructed.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Nail Yeast KOH Preparation

Frequently asked questions

Does a positive result mean I have Candida?
It means yeast was seen in the nail sample, but the organism is not always identified by this examination alone. Yeast identified in a nail may represent Candida, but culture or additional testing may be needed to confirm the species.
Can this test rule out a fungal nail infection?
No. A negative result means yeast was not detected, but a fungal infection may still be present. Repeat examination, fungal culture, or testing for dermatophytes may be needed if symptoms continue.
Is the KOH nail test painful?
The laboratory portion is not painful. Collecting a nail sample may cause brief discomfort or minor bleeding if the nail is very thick or fragile, but no anesthesia is usually needed.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy