Diarrhea is loose or liquid stool, passed three or more times a day. It ranges from mushy, falling-apart pieces to completely watery liquid with no solid matter at all. But beyond just “loose,” diarrhea can vary widely in color, texture, and other visual features, and those differences sometimes reveal what’s causing it.
The Two Main Types of Diarrhea Stool
The Bristol Stool Chart, a medical tool used to classify stool consistency, places diarrhea into two categories. Type 6 is fluffy, mushy pieces with ragged edges. It holds some shape but falls apart easily. Type 7 is entirely liquid with no solid pieces at all. Most bouts of diarrhea from a stomach bug or food intolerance fall somewhere between these two, and the consistency can shift from one bowel movement to the next.
Normal stool that’s simply soft isn’t diarrhea. The key distinction is that diarrhea has lost most of its form and often comes with urgency. Breastfed babies are a common source of confusion here: their normal stools are naturally loose, runny, and seedy with a yellow or sometimes green color. That’s not diarrhea. In infants, diarrhea means a sudden increase in both the number and looseness of stools, especially if mucus, blood, or a foul smell appears.
What the Color Tells You
Brown diarrhea is the most common and usually signals a routine infection or dietary trigger. But diarrhea can show up in a surprising range of colors, each pointing to something different happening in your digestive tract.
- Green: Food is moving through your intestines too quickly for bile (a digestive fluid that starts out green) to fully break down. Bacterial infections and irritable bowel syndrome can both cause this.
- Yellow: Often means excess fat in the stool. This can be a sign of conditions that impair fat absorption, such as celiac disease or problems with the pancreas.
- Pale, clay-colored, or gray: Suggests a lack of bile reaching the intestines. This points to issues with the liver, gallbladder, or bile ducts. Some anti-diarrheal medications can also cause this.
- Red: Bright red typically means bleeding in the lower digestive tract, from hemorrhoids, anal fissures, ulcers, or inflammatory bowel disease.
- Black: This one needs careful attention. Jet-black, tarry, sticky stool with a strong offensive odor (called melena) signals bleeding higher in the digestive tract, like the stomach. However, iron supplements, Pepto-Bismol, activated charcoal, and even large amounts of dark foods like blueberries or black licorice can stain stool black without any blood. The difference: medication-stained stool won’t have that tarry stickiness or the distinctive foul smell that comes from digested blood.
Greasy, Floating Stool
Some diarrhea looks distinctly oily or greasy rather than simply watery. This type, caused by fat malabsorption, tends to be bulky, foamy, and pale (clay-like). It often floats and is notoriously hard to flush. The smell is stronger than typical diarrhea. If your loose stool consistently looks greasy or leaves an oily film in the toilet, your body may not be properly digesting fats, which can stem from pancreatic insufficiency, celiac disease, or other digestive conditions.
Mucus in Diarrhea
Your intestines naturally produce a small amount of clear, jellylike mucus to keep the colon lining lubricated. You normally wouldn’t notice it. But during diarrhea, especially from intestinal infections, larger amounts of visible mucus can appear mixed in with liquid stool. It looks like clear or whitish jelly-like streaks or blobs. Mucus that’s bloody or accompanied by significant abdominal pain can indicate more serious inflammatory conditions like Crohn’s disease or ulcerative colitis.
When Diarrhea Has a Distinctive Smell
All stool has an odor, but certain types of diarrhea produce smells that are hard to ignore. C. diff infections, a common cause of diarrhea after antibiotic use, produce stool that’s typically mushy or porridge-like (not fully liquid) and sometimes greenish. What makes it distinctive is the smell: unusually strong and oddly sweet, caused by elevated bile acids in the stool. The stool may also contain visible blood, mucus, or pus.
Fatty stool from malabsorption also carries a particularly foul odor, distinct from typical diarrhea. If the smell of your diarrhea is notably different from what you’d expect, that’s useful information to share with a healthcare provider.
How Diarrhea Looks Different in Babies
Parents often struggle to tell the difference between normal infant stool and actual diarrhea because baby poop is naturally soft. Formula-fed babies typically produce yellow stool that’s thick, roughly the consistency of peanut butter. Breastfed babies produce stool that’s runny, seedy, and yellow to green. A water ring around the stool on the diaper is normal for breastfed infants.
Diarrhea in a baby means a sudden jump in how often and how loose the stools become compared to that baby’s baseline. If three or more stools in a row are noticeably more watery than usual, or if you see mucus, blood, or a bad smell, that’s diarrhea. Because babies dehydrate faster than adults, signs to watch for include no wet diapers for three hours or more, no tears when crying, a sunken soft spot on the skull, and unusual drowsiness.
Signs of Dehydration to Watch For
What diarrhea looks like in the toilet matters, but what it’s doing to your body matters more. Frequent watery stools pull fluid and electrolytes out fast. In adults, early dehydration shows up as extreme thirst, dry mouth, dark-colored urine, and urinating less than usual. As it progresses, you may feel dizzy or lightheaded, and your skin may lose elasticity. You can test this by pinching the skin on the back of your hand: if it doesn’t flatten back right away, you’re likely dehydrated. Sunken eyes or cheeks are another visible sign.