What Causes Light-Colored (Pale) Stool?

Ask a Doctor

Over the last month, no matter what I eat, my poop has been a light yellow color. I don’t have any other symptoms, but it’s odd to the point it’s worrying me. What does it mean when you have yellow poop? What is considered pale-colored stool?

Doctor's Response

If this is a persistent issue, you should consult a doctor and get some tests to rule out serious conditions. Without being able to examine the exact shade of your stool, I can say it makes a difference whether it is bright yellow, or more pale gray.

Stool that is yellow may suggest presence of undigested fat in the stool. This can occur as a result of diseases of the pancreas that reduce delivery of digestive enzymes to the intestines (pancreatic insufficiency), such as:

Celiac disease: Another condition that possibly may cause yellow and greasy stool is celiac disease (a malabsorption syndrome).

The digestive enzymes released from the pancreas and into the intestines are necessary to help digest fat and other components of food (proteins, carbohydrates) in the intestines so that they can be absorbed into the body. If the pancreas is not delivering enzymes into the intestines, then components of food, especially the fat, can remain undigested and unabsorbed. The stool containing the undigested fat may appear yellowish in color, greasy, and also may smell foul.

Ingestion of very high fat foods also can cause yellow, soft, and foul smelling stools.

Weight loss medications such as orlistat (Xenical, alli) work by limiting the amount of fat absorbed by the intestines. This can lead to bulky, yellow, and greasy stools.

However, stool can be gray or clay-colored if it contains little or no bile. The pale color may signify a condition (biliary obstruction) where the flow of bile to the intestine is obstructed, such as obstruction of the bile duct from a tumor or gallstone in the duct or nearby pancreas. The change of stool color to gray or clay typically occurs gradually as these medical conditions progress relatively slowly and stool becomes pale over time.

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Penner, R, M, MD, et al. Patient education: Blood in the stool (rectal bleeding) in adults (Beyond the Basics)." UpToDate. Sep 06, 2018.