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Yeast, Potassium Hydroxide Preparation — Qualitative

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

A microscopic examination that uses potassium hydroxide (KOH) to look for yeast in a collected specimen.

Quick summary

["A positive result means yeast was seen in the specimen and may support a yeast-related infection."]

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

Key facts at a glance

LOINC
55315-6
Short code
Yeast Spec Ql KOH Prep
Synonyms
Yeast Spec 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 is a qualitative laboratory test that examines a specimen for yeast under a microscope. Potassium hydroxide, often called KOH, helps clear away cellular material so yeast and related fungal structures can be seen more easily.

Why might I need this test?

This test may be ordered when a healthcare professional suspects a yeast infection, particularly when symptoms affect the skin, hair, or nails. It can also help distinguish yeast from other causes of similar symptoms.

How is the test performed?

A clinician collects a small sample from the affected area and mixes it with KOH. A laboratory professional then examines the prepared sample under a microscope to look for yeast.

How do I prepare for the test?

Follow the specific collection instructions provided by your healthcare professional. Do not apply creams, ointments, or other products to the area immediately before collection unless instructed, because they may interfere with the examination.

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

KOH preparation for yeast

Frequently asked questions

Does a positive result mean I have a yeast infection?
It means yeast was seen in the sample, but your healthcare professional must interpret this along with your symptoms and other findings. Some yeasts normally live on the skin, so the result alone may not establish an infection.
Is this the same as a fungal culture?
No. A KOH preparation is a rapid microscopic examination that can identify yeast, while a culture allows organisms to grow and can identify them more specifically.
What if the result is negative?
A negative result means yeast was not seen in the examined sample. If symptoms persist, your clinician may consider additional testing, such as a fungal culture.
  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