A bowel transit time test measures how long it takes for food to travel from your mouth through the digestive system to your anus. After you chew and swallow your food, it moves into your stomach, where it is mixed with acid and digestive enzymes. After your food leaves your stomach, it moves through your small intestine, where nutrients are absorbed for use by your body. The food then goes into your large intestine (colon) where water is absorbed. Whatever hasn't been digested and absorbed by your intestines combines with bacteria and other waste products and becomes stool (feces). Stool is expelled from your body through your anus.
Sometimes, just the time it takes for food to travel through the colon is measured. This is called the colonic transit time.
Bowel transit time depends on what types of food you eat and how much you drink. For example, people who eat lots of fruits, vegetables, and whole grains tend to have shorter transit times than people who eat mostly sugars and starches. Because different people have different transit times, experts disagree about how useful this test is.
For this test, you swallow one or more gel capsules filled with markers that will show up on an X-ray. When you will have X-rays depends on the type of test done. You may have an X-ray a few days later. Or you might take capsules several days in a row and have X-rays on multiple days to check the progress of the markers through your digestive system.
Why It Is Done
Bowel transit time tests may be done to:
- Find the cause of constipation or the slow movement of food through the digestive system.
- See if one place in your intestines is slowing down movement more than the rest of your intestines.
Bowel transit time tests are not done to find the cause of diarrhea.
How To Prepare
You may need to change your diet for a few days before having this test. You may also need to stop taking medicines for a short time before having a bowel transit time test. Tell your doctor about all the prescription and nonprescription medicines you are taking.
How It Is Done
Your doctor will give you one or more gel capsules filled with markers that will show up on an X-ray. Follow your doctor's instructions about when to take the capsules. You may take only one capsule. Or you may be told to take one at a certain time for 2 or 3 days in a row. You will then have X-rays taken of your digestive system. These are usually done on day 5. The number of markers that show up on the X-ray tells your doctor if you have a normal bowel transit time.
How It Feels
Bowel transit time tests don't cause pain. You will not feel discomfort from the X-rays used for the test. The X-ray table may feel hard, and the room may be cool.
Risks
This test is not recommended if you are pregnant. That's because the markers in the capsules and the radiation from the X-ray can harm your developing baby (fetus).
Results
Bowel transit time depends on what types of food you eat and how much you drink. The more markers that stay in your digestive system after 5 days, the slower your bowel transit time. Because different people have different transit times, experts disagree about how useful this test is.
Normal:
Less than 20% of the markers show up on an X-ray after 5 days (120 hours).
Abnormal:
More than 20% of the markers show up on an X-ray after 5 days (120 hours).
Credits
Current as of: October 6, 2025