A stool sample is needed.

There are many ways to collect the sample. You can collect the sample:

• On plastic wrap: Place the wrap loosely over the toilet bowl so that it is held in place by the toilet seat. Put the sample in a clean container given to you by your health care provider.
• In a test kit that supplies a special toilet tissue: Put the sample in a clean container given to you by your provider.

Do not mix urine, water, or toilet tissue with the sample.

For children wearing diapers:

• Line the diaper with plastic wrap.
• Position the plastic wrap so that it will prevent urine and stool from mixing. This will provide a better sample.
• Put the sample in a container given to you by your provider.

Make sure you follow your provider's instructions for returning the sample. Return the sample to the lab as soon as possible.

The stool sample is sent to a lab where a small amount is placed on a slide. The slide is placed under a microscope and checked for the presence of bacteria, fungi, parasites, or viruses. A stain may be placed on the sample that highlights certain germs or cells under the microscope.

There is no preparation needed.

There is no discomfort.

Your provider may order this test if you have severe diarrhea that will not go away or that keeps returning. The test result may be used to select the correct antibiotic treatment.

A normal result means there are no disease-causing germs or abnormal cells present.

Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your test results.

An abnormal result means that abnormal germs or cells have been found in the stool sample. This may be due to an infection of the digestive tract.

There are no risks associated with a fecal smear.

Stool smear

DuPont HL, Okhuysen PC. Approach to the patient with suspected enteric infection. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 267.

Plourde AR, Beavis KG. Specimen collection and handling for diagnosis of infectious diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 66.

Siddiqi HA, Rabinowitz S, Axiotis CA. Laboratory diagnosis of gastrointestinal and pancreatic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 23.

Wojewoda CM, Stempak LM. Medical bacteriology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 57.

Updated by: Michael M. Phillips, MD, Emeritus Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.