Fecal Occult Blood Test

Fecal immunochemical test (FIT)

Sometimes called an iFOBT, this test looks for hidden blood in your stool and should be performed every year if you’re using it to screen for colorectal cancer. It is more sensitive and doesn’t require diet changes, so it’s usually preferred over gFOBT. Following your kit's instructions, you’ll collect a stool sample at home and mail it to the lab.

Guaiac fecal occult blood test (gFOBT)

Like a FIT test, gFOBT detects trace amounts of blood in the stool and should be done every year for screening. But this type of test can be affected by non-steroidal anti-inflammatory drugs, vitamin C, or eating red meat or raw produce, so you’ll have some restrictions in the days before your test. You’ll also need to take multiple stool samples for gFOBT. Due to these issues, this test is less commonly used.

Stool DNA test

This test combines looking for hidden blood along with DNA markers in your stool that might be released by precancerous polyps or colorectal cancer. As a screening test, stool DNA tests are recommended every three years. This type of stool test requires a full stool sample that’s collected at home.

Before the test

If you choose a FIT or stool DNA test, you won’t need to modify your diet before your test. However, if you chose a gFOBT, your doctor may have you:

• Stop taking non-steroidal anti-inflammatory drugs (NSAIDs) seven days before your test
• Stop taking certain supplements, such as those with iron
• Limit your vitamin C intake to no more than 250 mg each day—either through supplements or foods—for seven days
• Avoid eating certain raw fruits or vegetables
• Avoid eating red meats for three days, since these foods may contain traces of blood

If you have certain conditions that cause bleeding, like hemorrhoids or ulcers, if you have blood in your urine or if you’re on your period, blood could be detected on your screening test when it’s not really a sign of cancer or polyps. You should not take the test in these cases.

During the test

During your test, you’ll have a kit and instructions to guide you through each step. There are a few different ways to collect samples, and tests vary in the number of samples needed. But the general steps for most tests include:

• Carefully read your test kit instructions
• Fill out any information or cards needed to go with your samples
• Flush the toilet two to three times before you take your sample
• Use the tools provided to you—such as paper, tube, applicator, sticks, brushes, etc.—to take your stool sample and place it on the card or in the sample container provided
• Wash your hands thoroughly with warm water and soap
• If you’re taking a gFOBT, follow the instructions to repeat this process and take additional stool samples
• Place your sample in the envelope or sample bag and follow the instructions to deliver it to the lab

After the test

If you had any diet or medication restrictions before your test, you can resume your normal routine right after the test. You can expect to get the results from your test in about a week, but ask your doctor or lab for a specific timeline.