Understanding Stool Color: What's Normal and What Might Concern You

Stool color reflects diet, transit time, bile metabolism, and pathology. Normal = brown (stercobilin from bilirubin breakdown).

Color Guide

Color	Common Benign Causes	Potential Medical Concerns
Brown	Normal diet, bile metabolism	—
Green	Leafy greens, food coloring, rapid transit (diarrhea)	Infection, malabsorption, bile acid diarrhea
Yellow, greasy, foul	High fat intake	Malabsorption (celiac, chronic pancreatitis, cystic fibrosis), giardiasis
Black, tarry (melena)	Iron supplements, bismuth (Pepto-Bismol), black licorice, blueberries	Upper GI bleed (ulcer, gastritis, varices, Mallory-Weiss)
Bright red / maroon (hematochezia)	Beets, red gelatin, food coloring	Lower GI bleed (hemorrhoids, diverticulosis, colitis, angiodysplasia, cancer)
Clay / pale / acholic	Antacids (aluminum hydroxide), barium study	Biliary obstruction (stones, stricture, pancreatic cancer), hepatitis, cirrhosis
Silver	—	Carcinoma of ampulla (rare); barium + upper GI bleed

When to Seek Care

• Black/tarry or bright red stool not explained by diet/meds
• Pale/clay-colored stool
• Persistent change + abdominal pain, weight loss, fever
• Age >45 with new change (screening colonoscopy indicated)

One odd-colored stool after a known dietary cause is usually benign. Persistent or unexplained changes warrant evaluation.