How to Do a Fecal Occult Blood Test (FOBT)

This information will teach you how to collect stool samples at home for your fecal occult blood test (FOBT).

A FOBT is a lab test used to check your stool (feces) for occult blood. Occult blood is blood that can’t be seen just by looking at the stool sample. There are many reasons you may have blood in your stool. Your doctor or nurse will tell you why you are having the test.

You will collect samples of your stool for 3 days in a row. This increases the chance of finding blood, since the bleeding may not happen every day. If you do not have a bowel movement for 3 days in a row, talk with your doctor or nurse. He or she will talk with you about obtaining the 3 samples over a longer period of time.

Preparing for Your FOBT

Ask your doctor or nurse how many days before the test you should start to prepare. He or she will also give you any special instructions, which you can write in the area we’ve provided below. It’s important to follow the instructions below to be sure your test results are accurate.

  • Beginning 3 days before and during the time you are collecting your stool samples, avoid:
    • Red meat, such as beef, lamb, or liver
    • Raw fruits and vegetables
    • Vitamin C (ascorbic acid), such as fruit juices containing vitamin C and vitamin C supplements in doses higher than 250 mg per day
    • Antacids
    • Medications to stop diarrhea
    • Iron supplements
  • Most people will need to stop taking aspirin, other nonsteroidal anti-inflammatory drugs (NSAIDs), and vitamin E before and during the 3 day collection period. These medications may cause small amounts of blood to appear in your stool. Your nurse will give you a resource called Common Medications Containing Aspirin and Other Nonsteroidal Anti-inflammatory Drugs, which lists common medications that have these products in them. It also lists medications you can take instead. If you take aspirin to prevent a heart attack or stroke, do not stop taking it unless your doctor instructs you to.
  • If you have any of the following issues when you are planning to obtain your stool samples, talk with your doctor or nurse. He or she will probably tell you to wait to obtain your samples until the issue(s) have gone away.
    • Menstrual period. You may need to wait until 3 days after the bleeding has stopped.
    • Bleeding hemorrhoids (swollen veins in your anus)
    • Blood in your urine


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Collecting the Sample

 The Hemoccult side


You will need the following supplies:

  • Hemoccult® slide
  • Applicator stick
  • A clean, dry container
  • Wastebasket


  1. Gather your supplies and place them in the bathroom where you can reach them easily. Do not set the Hemoccult slide or applicator stick on the edge of the sink, bath tub, or toilet tank. They should not get wet. Always keep the Hemoccult slides at room temperature, away from heat and light.
  2. Open the large front flap of the Hemoccult slide. You may notice a light blue discoloration on the paper in the squares above boxes A and B, but it will not affect on the test. 
  3. You must collect the sample before your stool touches the water in the toilet. Use the clean, dry container to catch your stool.
  4. Take a sample with one end of an applicator stick. Apply a thin smear of stool inside the square marked “A” on the Hemoccult slide (see Figure 1).
  5. Use the stick to collect a second sample from a different part of your stool. Apply a thin smear of stool inside the square marked B.
  6. Throw out the stick in the wastebasket.
  7. Close the cover of the Hemoccult slide. Store it at room temperature, away from light, children, and pets.
  8. Empty the container that holds the stool into the toilet. Flush the remainder of your stool.
  9. Wash your hands. Wet your hands with warm water and then rub your hands with soap for at least 15 to 20 seconds. Rinse your hands well under warm running water.

Repeat these steps to collect your samples on days 2 and 3.

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After You Collect the Samples

You can store the samples on the Hemoccult slide for 5 to 7 days from the date of your first collection. Do not mail your stool samples. Your healthcare provider will tell you where to take your stool samples.

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Your Results

Your doctor or nurse will call you with your results, explain what they mean, and tell you what to do next.

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