Understanding stool colour: what brown, yellow, green, pale, red & black mean

What determines stool colour?

Normal stool is brown because of stercobilin, a breakdown product of bilirubin from bile. Three things shift the colour: how much bile is present, how fast stool moves through the gut (transit time), and what you ate or which supplements you take. Most day-to-day colour changes are harmless and food-related. A few are a signal to get checked. Colour alone is never a diagnosis; it is a clue to log and, when red flags apply, to bring to a doctor.

darmkompass tracks stool colour as neutral self-tracking. It does not interpret a colour as a disease. Red and black are routed to the red-flag pathway because they can indicate blood; see below.

Which colours are within the normal range?

• Brown (all shades): the normal range. Lighter or darker brown day to day is unremarkable.
• Green: often just fast transit (the bile has no time to fully break down) or leafy greens, iron, food colouring. Usually harmless on its own.
• Temporary food/supplement effects: beetroot and red food colouring can mimic red; iron supplements and bismuth (Pepto-Bismol) can darken stool toward black; spinach can green it.

The useful question is not the colour in isolation but: is it persistent, and is anything else going on (blood, fever, weight loss, pain)?

Which colours warrant attention?

• Pale / clay-coloured: can mean too little bile reaches the gut (bile-duct or liver context). Persistent pale stool should be checked.
• Yellow, greasy, floating, foul-smelling: can point to fat malabsorption (steatorrhoea). Worth evaluating if it recurs.
• Red: can indicate fresh blood from the lower GI tract. Once food causes (beetroot) are excluded, this needs medical review.
• Black, tarry, sticky: can indicate digested blood from the upper GI tract (melena), a red flag (iron/bismuth excluded). Prompt evaluation.

None of these confirms a condition by itself; they are reasons to get a clinical assessment, not conclusions.

When is stool colour a red flag?

More on the full red-flag pathway: red-flag symptoms: when to see a doctor.

How to document stool colour

When you log a bowel movement in darmkompass, you can record colour alongside the Bristol type. Log honestly over 14–28 days; a single odd colour says little; a pattern (or any red flag) is what matters for a doctor's assessment. Red and black are flagged automatically so they are not lost in the routine view.

When to see a gastroenterologist

Any of the red flags above, a persistent unexplained colour change, or abnormal colour combined with systemic signs warrants an appointment. Bring your log: colour, Bristol type, timing and accompanying symptoms make the conversation faster and more precise. darmkompass does not diagnose; it helps you spot and share patterns.