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

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.

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

You swallow 2 gelatin capsules filled with carmine red or another food marker with a meal. Then you observe your bowel movements and record how long it takes after the capsules are swallowed until the dye first appears. Keep track of how long it takes for the marker 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.

The test helps determine bowel function. Your doctor may ask you to record transit times as fiber is introduced into the diet.

The bowel transit time varies even in the same person. The first of the color should appear in the stool about 12 - 14 hours after it is taken. The last of the color will appear within 36 - 48 hours.

If the times are much longer, 72 hours or more, it may indicate a slowed bowel function. A high fiber diet should speed the bowel transit time up.

There are no risks.