Stool Test for Parasites: What to Expect

A stool test for parasites, usually called an ova and parasite (O&P) test, is a lab test that checks a sample of your stool under a microscope for parasites and their eggs. A clinician orders it when symptoms such as ongoing diarrhea or belly pain could be caused by a parasite, and because parasites don't show up in every bowel movement, you may be asked to collect more than one sample over a few days.

This page explains what the test looks for, how collection works, why one sample is sometimes not enough and what the results mean. It is general education, not a replacement for the instructions that come with your own test. Get It Prescribed does not order or sell lab tests.

What does a stool test for parasites look for?

MedlinePlus describes the O&P test as a check for intestinal parasites and their eggs (ova). On a lab order it may also appear as a stool O&P, parasitic examination (stool), stool sample exam or fecal smear.

The test can find two broad groups:

• Single-celled parasites, such as Giardia, Cryptosporidium and Entamoeba histolytica. MedlinePlus lists these as the most common intestinal parasites in the United States, often picked up from water.
• Worms and their eggs, such as roundworm, hookworm and whipworm. The CDC says a provider can examine a stool sample under a microscope to diagnose these soil-transmitted worms.

A stool culture is a different test. MedlinePlus explains that a culture looks for organisms, mainly bacteria, by growing them in the lab, and that an O&P exam is often ordered alongside it. Your clinician decides which tests you need.

Why would a clinician order a parasite test?

According to MedlinePlus, a clinician may order an O&P test when symptoms that could come from an intestinal parasite have lasted for a few days, including:

• Diarrhea
• Belly pain
• Blood or mucus in the stool
• Unusually foul-smelling, greasy stools that float
• Nausea and vomiting
• Gas
• Fever
• Weight loss

MedlinePlus adds that these symptoms sometimes go away on their own, so testing is not always needed. A test is more likely if symptoms are serious, if your immune system is weakened, or if you could have been exposed, for example by swallowing water from a stream or lake, traveling to a country where intestinal parasites are more common, or spending time around someone with an infection. The test may also be used to see whether treatment for a parasite has worked.

How to collect a stool sample

Your clinician or the lab gives you a container or kit with its own instructions, and those come first. You may receive more than one container, and MedlinePlus notes that each may have different instructions, so read everything before you start. The general steps MedlinePlus describes are:

1. Label the container with your name and the date and time of collection.
2. Catch the stool in a clean, dry container, or on plastic wrap or special paper placed over the toilet.
3. Keep urine, toilet paper and toilet water out of the sample.
4. Close the container tightly and wash your hands well with soap and water.
5. Return the container as instructed, and on time.

No special preparation is needed for the test itself, and MedlinePlus lists no known risks.

Why you may need more than one sample

Parasites and their eggs are not passed in every bowel movement. MedlinePlus explains that you may need to collect several stool samples over a few days, because parasites may not show up in your stool every day, and testing several samples increases the chance of finding them.

One worm is especially easy to miss. The CDC notes that ordinary stool exams often miss Strongyloides, so clinicians may ask for repeated samples, use specialized stool methods or order a blood test for antibodies. See strongyloidiasis symptoms and treatment for more.

Pinworm uses a different test

Female pinworms lay their eggs at night on the skin around the anus, so the usual test collects eggs from that skin rather than from a stool sample. MedlinePlus describes the tape test: pressing the sticky side of clear tape against the skin around the anus in the morning, before bathing, then giving the tape to a clinician to check for eggs. It may need to be done on three separate days. Our guide on how to do a pinworm tape test at home walks through each step. The CDC also lists looking for worms around the anus two to three hours after the person falls asleep, or checking samples from under the fingernails. For adults, see pinworm treatment for adults.

How long do stool test results take?

There is no single answer. Timing depends on the lab, the tests ordered and how many samples are needed, and collecting several samples over several days adds to the total time. Ask the clinician or lab who ordered the test when to expect results.

What do the results mean?

MedlinePlus explains the two outcomes:

• Negative (normal): no parasites or eggs were found. That can mean you don't have parasites, or that there weren't enough in the sample to show up. Your clinician may order another test or different tests.
• Positive (abnormal): parasites or eggs were found. The report also shows which parasite it is and how many were seen, and treatment depends on the type of parasite and your general health.

Your clinician interprets the result alongside your symptoms and history. A blood count showing raised eosinophils, a type of white blood cell, can also point toward a worm infection.

How much does a stool test for parasites cost?

There is no standard price. What you pay depends on the lab, the number of samples, which tests are ordered and your insurance coverage. Ask the ordering clinician or the lab for an estimate before the test.

What happens after a positive test?

Treatment depends on what the lab found. If a test confirms an intestinal worm covered by our medicines' labeling, a licensed provider can review a written health assessment through Get It Prescribed:

• Pinworm, roundworm, hookworm and whipworm are the labeled uses listed in the prescribing information for the brand-name mebendazole chewable tablet. See mebendazole.
• Intestinal strongyloidiasis is a labeled use in the prescribing information for the brand-name ivermectin tablet. See ivermectin.

Single-celled parasites such as Giardia are treated with different medicines that we don't provide, so your own clinician handles those. For an overview of every worm adults commonly get, see intestinal worms in adults.

There is a one-time $50 consultation fee; mebendazole costs $3.50 per capsule and ivermectin $3.00 per tablet, and the prescriber decides the quantity. The service is available in all 50 states and the District of Columbia, and some states require a live phone or video visit. A prescription is never guaranteed, and how it works shows each step. The medicines dispensed through Get It Prescribed are compounded preparations made by a licensed compounding pharmacy for an individual patient. Compounded preparations are not FDA-approved, and the FDA does not review them for safety, effectiveness or quality. They are not generics of, or substitutes for, the brand-name products.

See a clinician in person if you have blood in your stool, severe belly pain, signs of dehydration, a high fever or a weakened immune system.

Related questions

What is a stool test for parasites called?

It is usually called an ova and parasite test, or O&P. A lab order may also say stool O&P, parasitic examination (stool), stool sample exam or fecal smear.

How many stool samples are needed to test for parasites?

Often more than one. MedlinePlus explains that parasites may not appear in every stool, so a clinician may ask for several samples collected over a few days to improve the chance of finding them. Collect the number your clinician or lab asks for.

Can a stool test detect all parasites?

No. A negative result can mean there weren't enough parasites in the sample to see. Pinworm is usually found with a tape test instead, and ordinary stool exams often miss Strongyloides, which may need repeated or specialized stool tests or a blood antibody test.

How long does a stool test for parasites take?

It depends on the lab, the tests ordered and how many samples are needed. Ask the clinician or lab who ordered the test when to expect results.

What happens if a stool test finds worms?

Treatment depends on which parasite was found and on your general health. A clinician chooses the medicine. Pinworm, roundworm, hookworm and whipworm are the labeled uses of mebendazole, and intestinal strongyloidiasis is a labeled use of ivermectin.

Sources

• MedlinePlus: Ova and Parasite Test — what the test looks for, why it is ordered, how to collect samples and what results mean.
• MedlinePlus: Fecal culture — how a stool culture differs from an ova and parasites exam.
• MedlinePlus: Pinworm test — how the tape test is done.
• CDC: About Pinworm Infection — how pinworm is diagnosed.
• CDC: About Soil-transmitted Helminths — roundworm, hookworm and whipworm, and diagnosis by stool exam.
• CDC: Clinical Overview of Strongyloides — why ordinary stool exams can miss Strongyloides, and other tests used.
• DailyMed: mebendazole chewable tablet prescribing information — labeled uses: pinworm, whipworm, roundworm and hookworm.
• DailyMed: ivermectin tablet prescribing information — labeled uses: intestinal strongyloidiasis and onchocerciasis.
• FDA: Compounding and the FDA — Questions and Answers — what compounded preparations are and how they are regulated.