The color of your stool is primarily determined by what you eat and how much bile is present during digestion. Brown in any shade is normal. It gets that color from bilirubin, a pigment in bile that your liver produces to help digest food. When stool shifts to green, yellow, black, red, or pale white, the cause is usually something harmless like a food or supplement, but certain colors can signal a problem worth investigating.
Why Normal Stool Is Brown
Your liver continuously produces bile, a yellow-green digestive fluid that gets stored in your gallbladder and released into your small intestine when you eat. As bile travels through your digestive tract, bacteria break it down and change its color from green to yellow to brown. The final shade of brown depends on how long food spends in your intestines and what you’ve been eating, so some variation from day to day is completely normal.
Green Stool
Green stool is one of the most common color changes people notice, and it’s almost always harmless. The two main causes are diet and transit speed. Eating large amounts of leafy greens like spinach or kale, or consuming foods with green dye (think mint ice cream or flavored drink mixes), can turn your stool visibly green. Iron supplements are another frequent culprit.
The other common cause is that food moved through your large intestine faster than usual, often because of diarrhea. Bile starts out green, and it needs time in the intestine to be broken down into its final brown color. When transit is rapid, bile doesn’t fully break down, and the stool retains that greenish tint. If you’ve had a bout of loose stools and notice a green color, that’s the explanation. It typically resolves once your digestion returns to its normal pace.
Black Stool
Black stool has two very different explanations, and telling them apart matters. The harmless version comes from iron supplements, Pepto-Bismol (bismuth subsalicylate), activated charcoal, or eating dark-colored foods like black licorice, blueberries, or blood sausage. This type of staining produces a dark stool that looks and smells like normal poop.
The concerning version is called melena: jet-black, tarry, sticky stool with a distinctively strong, foul odor. That smell is a byproduct of blood being digested as it travels through your gastrointestinal tract. Melena signals bleeding somewhere in the upper digestive system, such as the stomach or upper small intestine. The blood darkens the longer it spends in the GI tract, which is why upper GI bleeding produces black stool rather than red. If your stool is black, sticky, and unusually foul-smelling, and you’re not taking any of the supplements or foods listed above, that warrants prompt medical attention. A simple stool test can confirm whether blood is present.
Red Stool
Red stool can look alarming, but food is a common cause. Beets, tomato soup, red gelatin, and anything with red food dye can color your stool enough to mimic the appearance of blood. If you recently ate any of these and feel fine otherwise, that’s likely the explanation.
When the red color actually is blood, the most common source by far is hemorrhoids, which are swollen veins in the rectum or anus. They often develop from straining during constipation and typically produce small amounts of bright red blood on the toilet paper or in the bowl. Anal fissures, which are small tears in the lining of the anal canal, cause similar symptoms and also tend to result from straining.
More serious causes of red or bloody stool include inflammatory bowel disease (conditions like Crohn’s disease and ulcerative colitis that cause chronic intestinal inflammation) and colorectal cancer. Blood mixed into the stool itself, rather than just on the surface, or blood accompanied by changes in bowel habits, unexplained weight loss, or abdominal pain, is worth getting evaluated.
Yellow or Greasy Stool
An occasional yellowish stool isn’t cause for concern, especially after eating a high-fat meal. But stool that is consistently yellow, greasy, pale, foul-smelling, and tends to float points to a condition called steatorrhea, which means your body is passing excess fat instead of absorbing it.
This happens when something interferes with fat digestion or absorption. The pancreas, small intestine, liver, and bile ducts all play roles in breaking down dietary fat, and problems with any of them can produce fatty stool. Chronic pancreatitis can reduce the pancreas’s ability to produce enough digestive enzymes. Celiac disease damages the lining of the small intestine and impairs nutrient absorption. Even infections like giardiasis, a parasitic gut infection, can temporarily cause yellow, greasy stools. If this pattern persists for more than a few days, it’s a sign your body isn’t processing fat properly and the underlying cause needs to be identified.
Pale, Clay-Colored, or White Stool
Pale or clay-colored stool is one of the less common color changes but one of the more medically significant. It means your stool is lacking bilirubin, the bile pigment responsible for the normal brown color. That usually points to a problem with the biliary system: the liver, gallbladder, or bile ducts.
Bile can be blocked or reduced by a wide range of conditions. Gallstones can physically obstruct the bile ducts. Hepatitis (whether viral, alcohol-related, or toxin-induced) inflames the liver and disrupts bile production. Cirrhosis, fatty liver disease, narrowing of the bile ducts, pancreatitis, and tumors affecting the liver, bile ducts, gallbladder, or pancreas can all reduce bile flow enough to produce pale stool. Cholestasis, a condition where bile flow slows or stops entirely, sometimes occurs during pregnancy as well.
Because so many of these causes require treatment, persistently pale stool shouldn’t be ignored, especially if it comes with dark urine, yellowing of the skin or eyes, or abdominal pain.
Stool Color in Babies
Stool color in newborns follows its own progression that can look surprising if you’re not expecting it. A baby’s first few bowel movements are meconium: thick, black, tarry stool that looks nothing like what comes later. This is entirely normal and clears within the first few days of life.
After meconium passes, stool color depends largely on feeding. Breastfed babies typically produce mustardy yellow stool. Formula-fed babies tend toward yellow-tan with hints of green. All varying shades of yellow, brown, and green are considered normal in infants. The colors to watch for in babies are the same ones that signal problems in adults: red (possible blood), black after the meconium phase has ended (possible digested blood), and white or pale gray (possible bile duct issue, which in newborns can indicate a condition called biliary atresia that needs early treatment).
When Color Changes Are Harmless
Most stool color shifts are temporary and directly traceable to something you ate, drank, or took as a supplement. A useful rule of thumb: if the color change lasts one or two bowel movements and you can identify a dietary explanation, it’s almost certainly nothing to worry about. Green from a spinach salad, black from an iron pill, red from beet soup. These all resolve on their own once the food or supplement clears your system.
The changes that deserve attention are the ones that persist for several days with no obvious dietary cause, or that come paired with other symptoms like pain, weight loss, fever, or a noticeable change in your usual bowel habits. Black tarry stool with a strong odor, red blood mixed into your stool, and persistently pale or clay-colored stool are the three color signals most likely to indicate something that needs medical evaluation.