Brown poop

Poop is brown because of bile. Your liver makes bilirubin from old red blood cells and sends it into the gut in bile; gut bacteria then convert it, and the end product gives stool its brown color. Every shade of brown, from light tan to dark brown, counts as typical. The shade shifts from day to day with what you eat and how much bile is in your gut, and none of that is a problem.

Know your usual brown: Stoolio places every scan on a six-shade Color Assessment, including light brown, brown and dark brown, and tracks it with your Bristol type and 12 visual readings. Your first three scans are free.

Why is poop brown?

It is a chain that starts with your blood. When red blood cells reach the end of their life, their hemoglobin is broken down into bilirubin. The liver passes bilirubin into bile, the yellow-green digestive fluid stored in the gallbladder. In the colon, gut bacteria convert bilirubin into urobilinogen, and most of that leaves the body as stercobilin. MedlinePlus sums it up: bile salts released into the stool give it its normal brown color.

The bacterial side of this was only pinned down recently. In 2024, researchers identified BilR, the gut-microbe enzyme that turns bilirubin into urobilinogen. It is nearly universal in healthy adults but less common in newborns.

Which shades of brown are normal?

All of them. Cleveland Clinic calls brown the ideal poop color for adults and notes that the shade of brown can vary. Mayo Clinic says all shades of brown, and even green, are considered typical. Cleveland Clinic also points out that stool color is usually a mix of brown, yellow and orange tones, with the yellow and orange coming from bile and bilirubin themselves.

Why the shade changes

• Bile levels. The amount of bile in your gut naturally rises and falls, which alone can cause slight color changes from day to day.
• Diet. Dark leafy greens, beets, blueberries, carrots and food dyes all tint stool. Most of the time, Cleveland Clinic says, a color change points to something you ate.
• Medicines and supplements. Iron tends to darken stool; bismuth (Pepto-Bismol) can turn it black.
• Transit. When stool moves quickly, bile has less time to break down, pushing color toward green or yellow.

When to check in with a clinician

Brown needs no follow-up. What matters is a change away from brown that lasts. MedlinePlus advises contacting your provider if your stools are not the normal brown color for several days. And some changes deserve prompt attention whatever the timing: black and tarry stool, red you cannot explain and pale or clay-colored stool.

What Stoolio looks at visually

Stoolio's Color Assessment reads each scan against six shades: pale, light brown, brown, dark brown, green and very dark. For most people, most scans land in the three browns, and that is the point of tracking it: once Stoolio has your usual shade, a run of very dark or pale readings stands out against your own baseline instead of against memory. Color sits alongside your Bristol type, a Stoolio Score and the other visual readings, such as shape, size and consistency. See the full poop color chart.

Sources

1. MedlinePlus. Stools - pale or clay-colored.
2. Cleveland Clinic. Clay Colored Stool (Pale Stool).
3. Kalakonda A, et al. Physiology, Bilirubin. StatPearls.
4. Hoilat GJ, John S. Bilirubinuria. StatPearls. 2023.
5. Hall B, et al. BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen. Nat Microbiol. 2024.
6. Cleveland Clinic. What Does My Stool (Poop) Color Mean?
7. Mayo Clinic. Stool color. 2024.
8. Cleveland Clinic Health Essentials. 4 Things That Cause Yellow Diarrhea. 2025.
9. Cleveland Clinic Health Essentials. Can Food Change the Color of Your Poop? 2025.
10. MedlinePlus. Bismuth Subsalicylate.