Not exactly dinner table conversation — but your stool is one of the most useful, most overlooked indicators of how your digestive system is doing. A quick look, every now and then, can tell you a surprising amount.
This isn't meant to replace a proper medical opinion. Think of it as a general guide — something to help you notice when it's worth picking up the phone and calling your doctor, rather than a diagnosis in itself.
What colour tells you
Stool colour mostly reflects bile from the liver and traces of what you've recently eaten. Here's a rough guide to what different colours can mean.
Brown — the healthy default
Various shades of brown are completely normal, reflecting bile breaking down fat during digestion. Slight variation in shade day to day is nothing to worry about.
Green
Often simply diet-related — leafy greens or food colouring are common culprits. If it's persistent and unrelated to diet, it may suggest food is moving through your gut faster than usual, sometimes linked to a digestive infection. Worth checking if it persists for several days.
Yellow
Greasy, foul-smelling, or floating yellow stool can suggest your body isn't fully processing dietary fat — sometimes just from a particularly rich meal, but if persistent, it can point to a liver or gallbladder issue affecting fat digestion. See a doctor if this continues beyond a day or two.
Black
Sometimes explained by iron supplements or certain medications. Otherwise, black stool can indicate bleeding higher up in the digestive tract. Worth a medical opinion, especially if there's no obvious dietary explanation.
Red
Often simply beetroot, tomatoes, or dragonfruit. But persistent red stool — particularly with a metallic smell — can point to bleeding lower in the digestive tract, including from haemorrhoids or, less commonly, colorectal cancer. If it's not diet-related and continues, see a doctor.
Pale or chalky
This one deserves attention. Pale, clay-coloured stool can mean a lack of bile reaching the digestive tract — often related to a problem with the liver, gallbladder, or bile ducts. Please see a doctor promptly if you notice this.
What shape and consistency tell you
Beyond colour, the texture and shape of stool is also informative — and there's a standard clinical reference for this called the Bristol Stool Scale, which doctors commonly use to describe and classify what they're seeing.
Separate hard lumps
Small, hard, pellet-like pieces that are difficult to pass. Suggests constipation — stool has been sitting in the digestive tract longer than ideal. Often related to low fibre intake, dehydration, or inactivity.
Lumpy, sausage-shaped
A firm, lumpy log that's still somewhat difficult to pass. Milder constipation than Type 1, but still worth addressing with more fibre and fluids.
Sausage-shaped with surface cracks
Smooth-ish with some surface texture, passes easily. This is considered the ideal, healthy stool type.
Smooth and soft
A smooth, soft, easy-to-pass log. Also considered normal and healthy.
Soft blobs with clear edges
Still within the normal range, though it can suggest you'd benefit from a bit more soluble fibre in your diet — leafy greens are a good place to start.
Mushy, ragged edges
Leaning toward loose stool. Occasional episodes aren't usually concerning, but frequent Type 6 stool may suggest mild diarrhoea or a digestive upset worth monitoring.
Watery, no solid pieces
Fully liquid stool — this is diarrhoea. If it persists beyond a day or two, or comes with dehydration, fever, or pain, it's time to see a doctor.
General rule of thumb: Types 3 and 4 represent the healthy middle ground. If you find yourself consistently at either extreme — very hard (Types 1–2) or very loose (Types 6–7) — it's worth looking at your fibre intake, hydration, and activity level first, and seeing a doctor if it doesn't improve.
When to see a doctor without delay: black or pale chalky stool, visible blood that isn't explained by diet, or any persistent change in bowel habit lasting more than a couple of weeks — especially alongside unexplained weight loss or fatigue.
Dr Cha Kar Huei
Consultant General Surgeon (Gastrointestinal, Bariatric & Robotic Surgery), Hospital Picaso