Normal stool is brown. All shades of brown, from light tan to dark chocolate, fall within the healthy range. Green is also considered typical. The brown color comes from bile, a digestive fluid produced by your liver. As bile moves through your intestines, enzymes chemically alter it, shifting its color from green to brown. When something disrupts that process, whether it’s food, medication, or a medical condition, your stool can change color.
Why Brown Is the Default
Your liver continuously produces bile, a greenish-yellow fluid that helps break down fats in the small intestine. As bile travels the length of your digestive tract, bacteria and enzymes break it down further, and its pigments gradually shift from green to yellow-brown to the familiar brown you see in the toilet. The final brown shade depends on how long food spends in your intestines, what you ate, and how much bile your liver produced. A lighter or darker brown from day to day is completely normal and rarely means anything on its own.
Green Stool
Green stool is common and almost always harmless. It happens for two main reasons. First, eating a lot of leafy greens, green food coloring, or green-colored supplements can tint your stool directly. Second, when food moves through your intestines faster than usual (during a bout of diarrhea, for example), bile doesn’t have enough time to fully break down from green to brown. The result is stool that looks green or greenish-brown. Since the Mayo Clinic considers all shades of green typical, an occasional green bowel movement on its own is not a concern.
Black or Tarry Stool
Black stool has both harmless and serious explanations, and the key difference is texture and smell. Iron supplements, activated charcoal, bismuth-based medications like Pepto-Bismol, black licorice, and blueberries can all turn stool black. In these cases, the stool looks dark but otherwise seems normal.
Black stool that is tarry, sticky, and foul-smelling is a different situation entirely. This appearance, called melena, signals bleeding in the upper digestive tract, typically the esophagus, stomach, or the first part of the small intestine. Blood that travels through the digestive system gets partially digested, turning it dark and giving it that distinctive tar-like consistency. A simple lab test can confirm whether blood is present, so if you’re unsure whether iron pills or something more serious is behind the color change, that question is easy to answer.
Red or Bloody Stool
Bright red in the stool can come from foods like beets, tomato sauce, red gelatin, or red food dye. These dietary causes are temporary and harmless, usually clearing within a day or two.
When actual blood is present, its appearance gives clues about its source. Bright red blood that coats or mixes with the stool typically comes from the lower colon or rectum. Hemorrhoids are the most common cause, particularly if you notice blood on the toilet paper or in the bowl after straining. Other possibilities include anal fissures, inflammatory bowel disease, or colorectal polyps. Because beets and other red foods can look remarkably similar to blood, doctors test the stool before making any diagnosis.
Pale, Clay, or White Stool
Pale or clay-colored stool stands out because it signals a specific problem: your stool isn’t getting enough bile. Since bile is what gives stool its brown pigment, anything that reduces bile production or blocks its flow will leave stool looking pale, putty-colored, or grayish-white.
The causes all involve the biliary system, the network connecting your liver, gallbladder, and pancreas. Gallstones are one of the more common culprits. They can physically block the bile duct, preventing bile from reaching the intestines. Liver infections like viral hepatitis or alcoholic hepatitis can reduce bile production. Narrowing of the bile ducts, cysts, cirrhosis, and tumors of the liver, bile ducts, or pancreas can also obstruct flow. Some medications cause pale stool as a side effect as well. Persistent pale stool that doesn’t resolve in a few days warrants prompt attention because many of these underlying causes need treatment.
Yellow or Greasy Stool
Stool that is yellow, greasy, unusually foul-smelling, and tends to float often contains excess fat, a condition called steatorrhea. Normal digestion breaks down dietary fat in the small intestine and absorbs it into the body. When that process fails, undigested fat passes into the stool, giving it a pale yellow or clay-like appearance, a looser texture, and a noticeably worse smell than usual.
Several conditions can interfere with fat digestion or absorption. Celiac disease damages the lining of the small intestine, making it less able to absorb nutrients including fat. Crohn’s disease can do the same. Pancreatic insufficiency, where the pancreas doesn’t produce enough digestive enzymes, is another common cause. Infections like giardiasis (a waterborne parasite) and bacterial overgrowth in the small intestine can also produce fatty, yellow stools. If you notice this pattern repeatedly rather than as a one-off after a very fatty meal, it’s worth investigating.
Stool Color in Babies
Newborn stool follows a predictable color progression that looks alarming if you’re not expecting it. In the first day or two, babies pass meconium: a sticky, tar-like substance that is dark green to black. This is entirely normal and clears within a couple of days as the baby begins feeding.
After that, stool color depends on how the baby is fed. Breastfed babies typically produce loose, mustard-yellow stool, sometimes with a seedy texture. Formula-fed babies tend to have slightly darker yellow or tan stool that is a bit firmer. Dark green stool in formula-fed infants is also common, usually from the iron in the formula, and is not a concern. The one color that is always abnormal in a baby is white or very pale grey, which can indicate a congenital problem with the bile ducts that needs early treatment.
Foods and Medications That Change Stool Color
Dietary and medication-related color changes are temporary and resolve once you stop the trigger. Common examples include:
- Leafy greens, green food dye: green stool
- Beets, tomato products, red food dye: red or reddish stool
- Blueberries, black licorice: dark or black stool
- Iron supplements: black or dark green stool
- Bismuth medications (Pepto-Bismol): black stool
- Activated charcoal: black stool
If you recently started a new medication or changed your diet and your stool looks different, give it a few days after stopping or adjusting. Stool that doesn’t return to its usual brown within that window, or that comes with symptoms like pain, diarrhea, or fever, is worth bringing up with a healthcare provider.
When Color Changes Matter
A single unusual-colored bowel movement after eating beets or taking Pepto-Bismol is rarely significant. What matters is persistence and context. Stool that stays an unusual color for more than a few days, keeps changing colors, or comes with other symptoms like abdominal pain, fever, diarrhea, unexplained weight loss, or dizziness is telling you something your body needs checked out. Black tarry stool and persistent pale or white stool are the two colors that most consistently point to conditions needing prompt evaluation, since they can indicate active bleeding or bile duct problems respectively.