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Giardia Antigen in Stool (Qualitative)

Published: August 9, 2026Updated: August 16, 2026

This test detects the presence of Giardia lamblia, a common intestinal parasite that can cause diarrhea, stomach cramps, and nausea. It helps identify infections in people who may have symptoms or are at higher risk.

Quick summary

["Check for Giardia parasite in stool to guide treatment if you have digestive symptoms."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
27265-8
Short code
Giardia Ag Stl Ql
Synonyms
Giardia Ag Stl Ql
Category
chemistry
Sample
stool
Container
Clean container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why This Test Matters

Giardia is a single-celled parasite that thrives in contaminated water or food. It can spread easily in places with poor sanitation, like daycare centers, camps, or areas with waterborne outbreaks. Detecting Giardia helps doctors confirm an infection and recommend appropriate treatment, such as medications to kill the parasite.

How the Test Works

The test uses a simple stool sample to look for specific proteins (antigens) produced by Giardia. If the parasite is present, the test will show a positive result. This method is quick and often done in a lab or even at a clinic on the same day.

Sample Collection

You’ll need to collect a fresh stool sample (usually one or two small samples) in a provided container. If you’re unsure how to do this, ask your healthcare provider for instructions. The sample should be delivered to the lab as soon as possible for best accuracy.

What to Expect Before the Test

No special preparation is needed for this test. You may want to avoid taking certain medications (like some antibiotics) that could affect the results, but always confirm with your doctor first.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Stool Giardia Test

Frequently asked questions

What does a positive result mean?
A positive result means Giardia antigens were found in your stool, indicating an active infection. This usually requires treatment with prescription medications to clear the parasite. Symptoms like diarrhea, bloating, or stomach pain may improve after treatment.
What does a negative result mean?
A negative result means no Giardia antigens were detected in this sample. However, if you still have symptoms, you may need to retest or your doctor might recommend other tests or further evaluation. Some infections can be intermittent, so multiple samples may be needed.
How long does it take to get results?
Results are typically available within 24 to 48 hours, depending on lab processing times. Your healthcare provider will discuss the results with you and help determine the next steps.
  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 16, 2026. · Read our editorial policy