July 6, 2026
Stool colour changes far more than most people expect, and almost all of that variation is normal. What you ate, how much you drank, how fast things moved through — all of it shows up in the colour.
This is the chart, followed by what each colour usually means. A single unusual colour is rarely meaningful. A recurring one is worth paying attention to.
| Colour | Common cause | When to act | Full guide |
|---|---|---|---|
| Brown (light to dark) | Normal bile breakdown | No action needed | Covered below |
| Yellow | Diet, fast transit, fat malabsorption | See a GP if persistent, greasy or strong-smelling | Yellow stool |
| Green | Leafy vegetables, fast transit | Usually harmless; monitor if persistent | Green poo |
| Orange | Carrots, sweet potato, beta-carotene; sometimes reduced bile | See a GP if persistent with no dietary explanation | Covered below |
| Pale / clay / grey | Reduced bile flow | Speak to a GP, especially with other symptoms | Pale stool |
| Black / tarry | Iron supplements, bismuth medicines; or upper gut bleeding | Same-day medical advice if unexplained | Black stool |
| Bright red | Beetroot and red dyes; haemorrhoids; lower gut bleeding | Medical assessment if unexplained or recurrent | Covered below |
Medium brown, most of the time — but the healthy range is wider than people assume, running from light tan to dark chocolate.
That brown comes from bilirubin, a pigment produced when the liver breaks down old red blood cells. Bile carries it into the intestine, and the longer it spends there, the darker the stool becomes. Which means colour reflects two things at once: what you ate, and how quickly it moved through. Both change daily.
Transit time is how long food takes to travel from your mouth to the toilet. It matters here because bile pigment keeps breaking down along the way. Fast transit means less breakdown, which is why rushed digestion often looks green or yellow rather than brown. More on transit time.
The normal range. Medium brown suggests typical bile processing and an unremarkable transit time. Light brown may reflect faster transit or a lower-fat diet. Dark brown is still normal, and can reflect slower transit or a higher-protein diet.
Often follows certain foods, or faster gut transit when bile has less time to break down. Persistently yellow, greasy or foul-smelling stool can suggest fat is not being absorbed properly. A one-off yellow stool is typically nothing. Read the full guide to yellow stool, or the guide to oily and greasy stool if it is also pale and floats.
Usually diet — spinach, kale and other leafy greens tint stool green, as do some food dyes. Green also appears when things move through the colon faster than usual, because bile salts have not had time to fully break down. Rarely a sign of anything serious unless persistent and accompanied by other symptoms. Read the full guide to green poo.
Most often beta-carotene from carrots, sweet potato, squash or apricots, and it can also follow certain supplements and antacids. Occasionally orange stool reflects bile not reaching the gut in normal amounts, in which case it tends to appear alongside pale stools rather than on its own. Persistent orange with no dietary explanation is worth mentioning to a GP.
Worth medical attention, particularly if it persists. Pale stool can indicate that bile is not reaching the intestine properly, which is associated with liver, gallbladder and bile duct conditions. If pale stool appears alongside yellowing skin or dark urine, seek medical advice without delay. Read the full guide to pale stool.
Black, tarry stool — medically called melaena — can indicate bleeding in the upper digestive tract and needs prompt review. But black stool after iron supplements, bismuth-containing medicines such as Pepto-Bismol, or a large amount of liquorice or very dark food is common and harmless. The distinction is texture and smell rather than colour. Read the full guide to black stool.
Can indicate bleeding lower in the digestive tract, haemorrhoids, or simply red food — beetroot is the classic culprit, along with red food dye and tomato-heavy meals. Unexplained bright red stool warrants medical assessment, particularly if it persists or comes with dizziness, abdominal pain or significant bleeding.
Diet is the most common reason colour shifts temporarily. Beetroot is the most dramatic example: its pigment passes through many people's digestive systems intact and produces alarming red stool that is entirely harmless. Blueberries and red wine can darken it. Spinach, kale and matcha turn it green. Turmeric, sweet potato and carrots push it orange-yellow. Artificial dyes in sweets, coloured drinks and processed food can produce a surprisingly wide range.
If a colour change follows a meal you remember and resolves within one or two bowel movements, food is almost certainly the explanation.
Colour is one signal among several. If yours is normal but something else has changed, the guides to consistency, shape, smell and the Bristol Stool Chart cover those.
Colour is one of the more accessible gut signals almost nobody tracks consistently, which means changes go unnoticed — or get forgotten before a medical appointment. The useful question is never "is this colour normal?" but "is this different from my normal, and for how long?"
Gutsi is a gut wellness monitor that logs colour, consistency, frequency and hydration cues day to day, so a change has a start date rather than a vague sense that something's been off. It is a consumer wellness product, not a medical device. It does not diagnose, test for or detect any condition — it notices patterns, which may help you have a more informed conversation with a healthcare professional.
Medium brown is generally considered typical, reflecting normal bile processing and a transit time of roughly 24 to 72 hours. That said, colour varies naturally from light tan to dark brown and is influenced heavily by diet, hydration and speed of transit. A range of browns is normal. It is persistent non-brown colours that are worth noting.
Yes, and that is entirely normal. A meal rich in leafy greens, a high-fat dinner or a change in hydration can all shift it temporarily. What matters is whether changes are persistent rather than occasional, and whether they appear alongside other symptoms such as abdominal pain, a change in bowel frequency, or unexplained weight loss.
Persistent pale or clay-coloured stool; black or tarry stool not explained by iron supplements, bismuth medicines or dark foods; and bright red stool not explained by haemorrhoids or red foods all warrant medical assessment. Yellow stool that is greasy, floats and smells strongly may indicate fat is not being absorbed, and is worth investigating if it recurs.
As a rough guide, a colour change that resolves within one or two bowel movements and follows a meal you can identify is almost always food. Something that persists beyond a few days with no dietary explanation is worth an appointment. Pale stool with dark urine or yellowing skin, and unexplained black or red stool, should not wait.
Stool colour is one of the body's more honest daily signals, and most people never pay it much attention. A useful starting point is simply noticing what your normal range looks like over a week or two.
The goal is not to hit a specific colour every day. It is to know your baseline, so that when something genuinely changes, you notice. A recurring non-brown colour with no obvious dietary explanation is the signal worth bringing to a healthcare professional.
This content is for informational purposes only and does not constitute medical advice. If you have concerns about your digestive health, please speak to a healthcare professional.
