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Vaginal Yeast, Qualitative — Potassium Hydroxide (KOH) Preparation

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

A vaginal fluid microscopy test that checks for yeast, which may help evaluate vulvovaginal candidiasis.

Quick summary

["This test looks for yeast in vaginal fluid to help evaluate itching, irritation, or discharge."]

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

Key facts at a glance

LOINC
55313-1
Short code
Yeast Vag Ql KOH Prep
Synonyms
Yeast Vag 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 qualitative test examines vaginal fluid for yeast using a potassium hydroxide (KOH) preparation. Yeast may appear as round cells or as branching structures called pseudohyphae.

Why might I need this test?

It may be ordered when you have vaginal itching, burning, redness, soreness, or an unusual vaginal discharge. Your clinician uses the result together with your symptoms and other findings to evaluate a possible yeast infection.

How is the test performed?

A clinician collects a small amount of vaginal fluid and examines it under a microscope after adding KOH. The preparation helps make yeast structures easier to see, and the result is reported as detected or not detected.

How do I prepare for the test?

Tell your clinician if you recently used vaginal medications, douches, creams, or suppositories, because these can affect the findings. Follow the instructions provided for the collection, and do not clean the vaginal area immediately beforehand unless you are told to do so.

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

Vaginal yeast (KOH preparation)

Frequently asked questions

Does a positive result mean I definitely have a yeast infection?
Not always. Yeast may be present without causing symptoms, and a positive result is interpreted along with your symptoms, examination, and other tests.
What is a KOH preparation?
KOH is a laboratory solution used to prepare vaginal fluid for microscopic examination. It helps clear some cellular material so that yeast and related structures are easier to identify.
Can medications affect the result?
Yes. Vaginal antifungals, douches, and other intravaginal products may reduce the number of yeast cells or obscure them, potentially affecting the result.
  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