The short answer
Healthy is deep brown, firm, and roughly daily. Green and yellow are usually diet or speed-of-transit and get a couple of days of watching. Black-tarry stool and real amounts of fresh blood are same-day vet calls, no watching. Moving white specks are tapeworms (routine visit), and a cat straining in the box producing nothing may have a urinary blockage, which is an emergency. When in doubt: take a photo and call your vet, since this article is general information, not a diagnosis.
The two now-colours, plus one non-colour emergency
Black and tarry means digested blood from the upper GI tract. More than a streak of fresh red blood means active bleeding lower down. Both are same-day vet calls. One green-specific exception skips the watching window too: if the plant your cat nibbled could be a lily, call your vet or Pet Poison Helpline right away, since every part of a true lily can cause acute kidney failure in cats. And one thing the colour chart cannot show: a cat straining in the box and producing nothing may be blocked, and a urinary blockage is a life-threatening emergency within hours, especially in male cats.
The litter box is the one health monitor every cat owner checks daily whether they mean to or not. Colour is genuinely informative, most changes have mundane explanations, and the dangerous ones are easy to recognize. The chart below covers what each colour usually means, what it can mean, and where the vet-call line sits, based on standard veterinary guidance from sources like VCA Animal Hospitals and the Cornell Feline Health Center.
The colour chart
| Colour | Usually means | Worth watching for | Call the vet |
|---|---|---|---|
| Deep brown | Normal. The healthy baseline. | Nothing, if it is firm, log-shaped, and consistent day to day. | No action needed. |
| Black and tarry | Digested blood from the stomach or upper intestine. | Do not wait and watch. Black, sticky, tar-like stool suggests internal bleeding. | Now. Same-day vet or emergency clinic. |
| Red streaks or fresh blood | Bleeding low in the GI tract: colitis, constipation straining, or irritation. | A single small streak in an otherwise normal cat can be minor. Repeated blood, blood with diarrhea, or a cat that is hiding or off food is urgent. | Same day if it repeats or the cat seems off; immediately if there is a lot of blood. |
| Green | Food moving through fast, or plant material (grass, houseplant nibbling). | Green with vomiting or lethargy, or if a nibbled houseplant might be toxic (lilies are an emergency for cats). | Persists past a couple of days, or any chance of a toxic plant. |
| Yellow or orange | Food moving through too quickly; diet change or intolerance. | Repeated yellow stools, or yellow with poor appetite. Persistent cases can point at liver or gallbladder issues. | Persists past a couple of days or pairs with appetite loss. |
| White or grey | Greasy grey suggests fat maldigestion; chalky pale stool can follow a heavy-bone raw diet. | Persistent pale, greasy stools deserve a workup. | Persistent grey needs a vet look; raw-diet white is a diet conversation. |
| White specks that move | Worms, most often tapeworm segments that look like rice grains near the tail or in the box. | No watching needed; this one is diagnostic on sight. | Book a routine visit for deworming; bring a photo or sample. |
| Coated in mucus | Large-intestine irritation, often stress colitis or a diet change. | Occasional mucus resolves on its own. Persistent mucus, or mucus with blood or diarrhea, does not. | If it lasts more than a few days or pairs with blood or diarrhea. |
The litter box tells you more than colour
Consistency and frequency carry as much signal as colour. The healthy baseline is a firm, scoopable log roughly once a day. Watery diarrhea beyond a day or two is a vet call, and so is the opposite: hard, dry pellets with visible straining, which in cats often traces back to dehydration or hairballs, per VCA. A cat that starts going outside the box is also communicating; our litter box problems guide covers that vet-first troubleshooting.
Since cats hide illness instinctively, the box is often the earliest warning you get. Pair any stool change with a quick check of the basics: eating, drinking, energy, hiding. A colour change alone in a cat acting normally is usually a watch; a colour change plus a behaviour change moves the timeline up. And take a photo of anything strange, since it gives your vet far more than a description over the phone.
This article is general information, not veterinary advice. When in doubt, call your vet.
Thinking about adding a cat to the family?
Browse adoptable rescue cats and kittens from shelters and foster networks across Canada, searchable in one place.
Browse Adoptable Cats →Frequently Asked Questions
What does black cat poop mean?
Black, tarry, sticky stool is the one colour that should always trigger a same-day vet call, because it typically means digested blood from the stomach or upper intestine. Causes range from ulcers to swallowed objects to clotting problems, and none of them are wait-and-see. Do not confuse it with dark brown: melena is distinctly black and tar-like.
Why is there blood in my cat's poop?
Fresh red blood comes from low in the GI tract. A single small streak in a normal, happy cat is often minor irritation from straining or constipation. Repeated blood, blood mixed with diarrhea, more than a streak, or a cat that is hiding, off its food, or straining in the box means a same-day call. Cats hide illness well, so visible blood plus any behaviour change is worth taking seriously.
Why is my cat's poop green?
Usually plant material (grass or houseplant nibbling) or food moving through quickly. The exception that matters for cats: if the nibbled plant could be toxic, and lilies in particular are a life-threatening emergency for cats, call your vet immediately rather than watching the litter box. Otherwise, green that persists past a couple of days or arrives with vomiting or lethargy deserves a vet call.
Why is my cat's poop yellow?
Yellow usually means food is moving through faster than bile can be fully processed, most often after a diet change or a food intolerance. One or two yellow stools in an otherwise happy cat is a watch-and-wait. Repeated yellow or orange stools, or yellow with appetite loss, can point at liver or gallbladder issues, and that combination is worth a vet visit.
What do white specks in cat poop mean?
Moving white specks that look like rice grains are tapeworm segments, one of the most common findings in the litter box, especially in cats that hunt or have had fleas. It is diagnostic on sight: book a routine vet visit for deworming and bring a photo or a sample. Indoor-only cats get tapeworms too, usually via fleas.
Why is there mucus on my cat's poop?
A slimy coating usually means the large intestine is irritated, and stress is the classic feline trigger: a move, a new pet, renovations, or a routine change. Occasional mucus in an otherwise normal cat typically resolves within a few days. Persistent mucus, or mucus alongside blood or diarrhea, is a vet visit.
How long should I wait before calling the vet about abnormal cat poop?
Two rules. Black-tarry stool and significant fresh blood skip the waiting: call the same day. For everything else (green, yellow, mucus, soft stool), a couple of days of watching is reasonable in an adult cat that is eating, drinking, and behaving normally. Kittens, seniors, and any cat that is also vomiting, hiding, or off its food get a much shorter window: call within a day. And a cat straining in the box producing nothing may have a urinary blockage, which is an emergency, not a stool question.
What should healthy cat poop look like?
Deep brown, log-shaped, firm enough to scoop cleanly, and produced roughly daily. Consistency matters as much as colour: watery diarrhea beyond a day or two, or hard dry pellets with straining, are both worth attention even in a normal colour, per VCA. Since you scoop the box anyway, you already have the best health-monitoring habit in cat ownership; changes from your cat's normal are the signal.
Dog Poop Colour Chart
The canine version, colour by colour.
Litter Box Problems
Vet-first troubleshooting when the box stops being used.
Cat-Proofing Your Home
Toxic plants (incl. lilies), strings, and the swallow hazards.
Adoptable Cats Across Canada
Cats and kittens from rescues coast to coast, in one place.