Why does my poop change color every few days?

Stool color can change every few days, and in many cases that’s normal. The most common reasons are what you eat, how fast food moves through your gut, and medications or supplements.

Common reasons stool color changes

• Diet: Foods and food dyes can change stool color quickly. For example:
  • Green: leafy greens, green food coloring
  • Red: beets, red food dye
  • Black or very dark: iron supplements or bismuth subsalicylate (Pepto-Bismol)
• Bile and digestion speed: Bile is made by the liver and helps digest fat. It starts out greenish and normally turns stool brown as it’s broken down during digestion.
  • If stool moves through too quickly, it may stay greenish or yellowish.
  • If digestion is normal, stool is usually brown.
• Medications/supplements: Iron, Pepto-Bismol, and some antibiotics can change stool color.

When to get checked

Some color changes can signal a medical problem, especially if they persist:

• Black, tarry stool: can mean bleeding in the upper GI tract, unless explained by iron or Pepto-Bismol
• Bright red stool: can mean bleeding in the lower GI tract or hemorrhoids, though it can also come from foods like beets or red dye
• Pale, white, or clay-colored stool: can mean there isn’t enough bile reaching the stool and should be evaluated

If the color change keeps happening, or you also have abdominal pain, fever, diarrhea, vomiting, or unexplained weight loss, it’s a good idea to see a healthcare provider.