This page is educational, not diagnostic. Black/tarry or red/bloody stool warrants prompt medical attention — don't wait to "see if it happens again."
Stool color is a genuinely useful, clinically relevant indicator of gastrointestinal and hepatobiliary health. Normal brown color comes from stercobilin, a pigment produced as bile breaks down during digestion — so color changes usually mean something upstream (diet, bile flow, transit speed, or bleeding) has changed. This is one of the factors PooDoo's Digestive Health Score weighs alongside your Bristol Stool Chart type.
Brown – Normal
The default, healthy color. Indicates normal bile production and typical intestinal processing. Shades can vary day to day with diet and hydration — that's expected.
Green
Usually harmless. Most often caused by eating a lot of leafy greens or green food coloring, iron supplements, or stool moving through the colon faster than usual (so bile hasn't fully broken down into its normal brown pigment yet). If it's persistent alongside diarrhea or pain, it's worth mentioning to a doctor, but an occasional green day on its own usually isn't a concern.
Yellow / Greasy
Pale yellow, greasy, or foul-smelling stool that's hard to flush can indicate excess fat in the stool — sometimes a sign the body isn't fully absorbing fat, which can relate to bile flow or pancreatic function. Occasional yellow stool after a very rich or fatty meal usually isn't significant; a recurring pattern is worth a conversation with a doctor.
Pale / White (Acholic Stool)
May indicate reduced or absent bile flow, commonly associated with biliary obstruction or liver disease. This is one of the colors PooDoo flags as critical — if you see consistently pale or clay-colored stool, especially with yellowing skin/eyes or dark urine, seek medical advice.
Black (Melena)
Typically suggests upper gastrointestinal bleeding, where blood has been digested as it passes through the GI tract — this is a distinct, tar-like black, not just a dark brown. (Iron supplements and bismuth medications like Pepto-Bismol can also darken stool, which is harmless — but if you haven't taken either, black stool needs prompt medical attention.)
Red (Hematochezia)
Indicates lower gastrointestinal bleeding, as defined in clinical guidelines from the British Society of Gastroenterology. Red food coloring or beets can mimic this — but if you can't explain it by something you ate, treat it as something to get checked.
See the shape too
Color is only one signal. Pair it with stool shape and consistency on the Bristol Stool Chart, or read the full scoring methodology to see how PooDoo combines both.