Normal stool is brown, and the shade can range from light tan to dark chocolate depending on your diet. That brown color comes from a pigment called stercobilin, which is produced when bacteria in your gut break down bile. When something disrupts that process, whether it’s a food you ate, a medication, or a medical condition, stool color shifts. Here’s what each color typically signals.
Why Stool Is Brown in the First Place
Your liver produces bile, a yellow-green fluid that helps digest fats. As bile travels through your digestive tract, gut bacteria chemically transform it through several steps: first into a compound called urobilinogen, then eventually into stercobilin, a dark orange-brown pigment. This pigment is what gives stool its characteristic color. Any change in bile production, bile flow, gut bacteria, or transit speed can alter this chain and shift the color of your stool.
Green Stool
Green stool usually means one of two things: you ate something very green, or food moved through your intestines faster than usual. Bile starts out yellow-green and only turns brown after enzymes and bacteria have enough time to process it. When you have diarrhea or anything else that speeds up digestion, bile doesn’t fully break down, and stool stays green.
Common non-medical causes include leafy green vegetables (spinach, kale), green food coloring in drink mixes or ice pops, and iron supplements. If you can trace the color to something you ate and it resolves within a day or two, it’s almost always harmless.
Black Stool
Black stool has two very different explanations, and telling them apart matters. The harmless version comes from foods and supplements: iron pills, black licorice, blueberries, activated charcoal, or bismuth-based medications like Pepto-Bismol can all turn stool black.
The concerning version is tarry, sticky, and has a distinctly foul smell. This appearance, called melena, indicates bleeding in the upper digestive tract, typically the esophagus, stomach, or the first section of the small intestine. Blood turns dark because it gets digested as it passes through the GI tract. Peptic ulcers are the most common cause of this type of bleeding. Other possibilities include tears in the esophagus from violent vomiting, inflamed stomach lining, swollen veins in the esophagus (often related to liver disease), and in rarer cases, cancers of the upper digestive tract.
If your black stool is tarry and foul-smelling and you haven’t taken any of the foods or medications listed above, treat it as urgent. A simple chemical test can confirm whether blood is present.
Red or Bloody Stool
Bright red blood in or on stool typically points to bleeding somewhere in the lower digestive tract: the colon, rectum, or anus. Hemorrhoids are the single most common cause. These swollen veins in the rectum or anus often bleed during bowel movements, especially with straining, and the blood is usually bright red and on the surface of the stool or on toilet paper.
Anal fissures, which are small tears in the lining of the anal canal, cause similar-looking bleeding along with pain. Beyond these common causes, red blood can also signal:
- Diverticulitis: infected pockets in the colon wall where small blood vessels can rupture
- Inflammatory bowel disease (IBD): conditions like Crohn’s disease and ulcerative colitis that inflame the intestinal lining
- Colon polyps or colorectal cancer: abnormal tissue that bleeds when irritated or damaged
- Infections: bacterial infections like E. coli or C. diff can cause bloody diarrhea
Keep in mind that beets, red gelatin, tomato soup, and red food dyes can all make stool look red without any bleeding involved. If you’re unsure whether what you’re seeing is blood, and especially if it persists beyond one or two bowel movements, it’s worth getting checked.
Pale, Clay, or White Stool
Pale or clay-colored stool is one of the more medically significant color changes. It means bile isn’t reaching your intestines in normal amounts. Since bile salts are what give stool its brown color, anything that reduces bile production or blocks its flow will leave stool looking pale, putty-colored, or almost white.
The biliary system, which includes the liver, gallbladder, and pancreas, is usually the source of the problem. Gallstones are a common culprit because they can physically block the bile ducts. Other causes include hepatitis (both viral and alcoholic), narrowing of the bile ducts, tumors of the liver, bile ducts, or pancreas, and certain medications. Persistent pale stool that lasts more than a couple of days is not something to wait on, because it often points to a condition that needs treatment.
Yellow and Greasy Stool
Yellow stool that looks greasy, floats, smells worse than usual, and is hard to flush is a sign of fat malabsorption. Your digestive system isn’t breaking down or absorbing fats properly, so undigested fat ends up in your stool. The medical term for this is steatorrhea.
People typically notice several changes at once: stool becomes bulky, loose, foamy, and lighter in color. Celiac disease is one of the more common underlying causes, since it damages the lining of the small intestine where fat absorption happens. Chronic pancreatitis, bile duct problems, and other conditions affecting the small intestine can also produce this pattern. An occasional yellow stool after a very high-fat meal isn’t necessarily a concern, but if it’s happening regularly, it suggests your body is consistently failing to process dietary fat.
Stool Color in Babies
Infant stool follows its own color timeline and the rules are different from adults. Almost all newborns pass meconium as their first stool: thick, black, and tarry-looking. This is completely normal and clears within the first few days of life.
Once feeding begins, stool shifts to green or yellow with a more liquid consistency. Breastfed babies tend to produce stool in the green-yellow-brown range for as long as they’re breastfeeding. Formula-fed babies produce stool in a similar palette, sometimes slightly lighter. In babies, the colors that warrant concern are the same as in adults: persistent white or clay-colored stool (which can indicate a biliary problem present from birth), red stool, or black stool after the meconium phase has passed.
Foods and Medications That Change Stool Color
Before assuming a color change means something medical, consider what you’ve consumed in the past 24 to 48 hours. Many color shifts are entirely diet-driven and resolve on their own.
- Green: spinach, kale, green food dyes, iron supplements
- Black: iron supplements, bismuth medications (Pepto-Bismol), activated charcoal, black licorice, blueberries
- Red: beets, tomato-based foods, red food dyes
- Orange: carrots, sweet potatoes, foods with beta-carotene
A useful rule of thumb: if a new stool color appeared right after eating a specific food or starting a new supplement and resolves within a day or two once you stop, the cause is almost certainly dietary. If the color change persists without an obvious dietary explanation, or if it’s accompanied by pain, weight loss, or changes in how you feel, that’s when the color becomes diagnostically meaningful.
Stool Shape and Consistency Also Matter
Color tells part of the story, but shape and texture add important context. The Bristol Stool Chart classifies stool into seven types based on form. Types 1 and 2, hard lumps or lumpy sausage shapes, indicate constipation. Types 3 and 4, sausage-shaped with cracks or smooth and soft, represent the ideal range. Types 5 through 7 progress from soft blobs to mushy pieces to fully liquid, indicating increasingly loose stool or diarrhea. A color change combined with a shift toward the extremes of this scale (very hard or very watery) gives a more complete picture of what’s happening in your digestive system than either characteristic alone.