Bowel transit time refers to how long it takes for the food to move from the mouth to the anus.

This article discusses the medical test used to determine bowel transit time.

The test helps determine bowel function.

Your doctor may ask you to record transit times you introduce fiber into your diet. Your diet affects the bowel transit time. For example, if you eat a lot of foods rich in fiber (whole grains, vegetables, and fruits), you have a more rapid transit time and a heavier, bulkier stool.

You will be asked to swallow two gelatin capsules filled with carmine red or another food dye. You take the special capsules with a meal.

Afterwards, you observe your bowel movements and write down how long it takes for the colored dye to first appear. You'll also need to note how long it takes for the color to disappear from the stools.

No preparation is usually needed. However, you should follow any diet or other directions from the health care provider.

You will not feel the capsules move through your gastrointestinal system.