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).

About Your 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 your stool. There are many reasons you may have blood in your stool. Your doctor or nurse will tell you why you’re having the test.

For your FOBT, 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 don’t have a bowel movement on one of the 3 days, talk with your doctor or nurse. They will talk with you about collecting the 3 samples over a longer period of time.

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Preparing for Your FOBT

Ask your doctor or nurse how many days before the test you should start to prepare. They may give you special instructions, which you can write in the “Notes” area at the end of this section. It’s important to follow the instructions below to be sure your test results are accurate.

  • Starting 3 days before you begin 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 milligrams (mg) per day
    • Antacids (medications to relieve heartburn or stomach pain, such as Tums®)
    • Medications to stop diarrhea (loose or watery bowel movements)
    • Iron supplements
    You can start eating these things again after your FOBT.
  • 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.
  • If you have any of the following  during the 3 days you’re planning to collect your stool samples, talk with your doctor or nurse. They may tell you to wait to collect your samples.
    • Menstrual period
    • Bleeding hemorrhoids (swollen veins in your anus)
    • Blood in your urine


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Collecting the Sample

Figure 1. The Hemoccult side


You will need the following supplies:

  • Hemoccult® slide
  • Applicator stick
  • A clean, dry container
  • Trash can


  1. Gather your supplies. Place them in the bathroom where you can reach them easily.
    • Remove the Hemoccult slide from its paper envelope. Set the envelope aside.
    • Don’t set the Hemoccult slide or applicator stick on the edge of the sink, bath tub, or toilet tank. They shouldn’t 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. The discoloration won’t affect the test.
  3. Sit on the toilet like you usually do to pass stool (have a bowel movement).  Use the clean, dry container to catch your stool before it touches the water in the toilet.
  4. Take a sample of your stool 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 and put it back into its paper envelope. Don’t put it in anything waterproof, such as a plastic bag. 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. Don’t mail your stool samples. Your healthcare provider will tell you where to take your stool samples.

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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