Normal
Brown poo
Normal. Brown comes from bile pigments broken down by gut bacteria.
Poo colour chart: what your stool colour means
Most colour changes come from what you ate and are harmless. A few — especially red and black — can signal bleeding and should always be checked by a doctor.
Emergency? Call 999 or go to A&E if you are passing a lot of blood, feel faint or dizzy, or are vomiting blood. For urgent advice in the UK, call NHS 111.
Normal
Dark Brown poo
Usually normal — can follow dark foods, coffee, red meat or mild dehydration.
Usually harmless
Green poo
Often leafy greens, food colouring, iron, or fast transit. Rarely a concern on its own.
Usually harmless
Yellow poo
Can follow fatty meals or fast transit. Persistent greasy, foul-smelling yellow stool is worth mentioning to a GP.
Speak to a GP
Pale poo
Pale or clay-coloured stool may mean bile is not reaching the gut. Speak to a GP, urgently if your skin or eyes look yellow.
Get checked promptly
Red poo
Red can mean blood. Beetroot and red food colouring can mimic it, but blood should always be checked by a doctor.
Get checked promptly
Black poo
Black, tar-like stool can mean bleeding higher in the gut. Iron tablets, bismuth and liquorice can also darken stool — get it checked.
Why poo is brown
Your liver makes bile to help digest fat. As bile travels through your gut, bacteria convert its pigments into stercobilin — which gives stool its brown colour. That’s why pale, clay-coloured stool can mean bile isn’t reaching the gut, and why colour can shift with how fast food moves through.
Foods and medicines that change colour
- Green: spinach, kale, green food colouring, iron supplements, fast transit.
- Red or pink: beetroot, red food colouring, tomato skins — but never assume; blood needs checking.
- Black: iron tablets, bismuth medicines (e.g. Pepto-Bismol), liquorice, blueberries.
- Yellow: fatty meals or fast transit; persistent greasy, foul-smelling yellow stool is worth mentioning to a GP.
Frequently asked questions
What colour should healthy poo be?
Healthy poo is usually medium to dark brown. The brown comes from bile pigments that gut bacteria break down.
Is green poo bad?
Usually not. Green poo often comes from leafy greens, green food colouring, iron supplements or food moving through quickly. It is rarely a concern on its own.
When is poo colour an emergency?
Red (possible blood) or black, tar-like stool should always be checked. Call 999 or go to A&E if you are passing a lot of blood, feel faint, or are vomiting blood.
Shape matters as much as colour — compare with the Bristol Stool Chart, and read when to see a doctor.