What this means
Blood looks different depending on where it comes from. Bright red streaks or drops on the stool point to bleeding in the lower part of the gut. Black, sticky, tar-like stool means digested blood from higher up in the digestive tract. In vomit the blood can be red or dark like coffee grounds. If you can, take a photo so your vet can see it.
There are many possible causes: an irritated or inflamed gut, parasites, swallowed objects that should not have been, something toxic, clotting problems or tumours. They cannot be told apart by looks, so even a small amount of blood needs to be looked into, and that does not rest on guessing or trying things at home.
Cats hide illness, so blood may be the first thing you notice while the cat itself looks bright. Do not wait for it to stop eating or turn weak. Do not try to give anything at home, and if your cat is straining in the litter box, look at the emergency signs below.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your cat.
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Inflammation or infection of the gut
An irritated gut wall can bleed, especially when a cat has diarrhoea or is vomiting. Blood may come with mucus.
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Parasites
Intestinal parasites sometimes cause bloody stools. Kittens are especially vulnerable.
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A swallowed object that should not have been
Thread, ribbon, plastic or sharp objects can injure the digestive tract and cause bleeding. Vomiting may come with it.
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Hard stools and straining
After long straining over hard stools, red blood can appear on them. The cause of the blood still has to be found by a vet.
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Something toxic
Some toxic substances can damage the gut or interfere with clotting and cause bleeding. It is worth telling your vet about this straight away.
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Tumours and other illness
Tumours of the gut, such as lymphoma, and some diseases of other organs can bleed. You will usually also see the cat losing weight or eating less.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- What colour the blood is: bright red, dark, or stools that are black
- How much there is and whether it is on the stool or mixed in it
- Whether your cat is vomiting, has diarrhoea or is straining
- Whether it eats, drinks and has its usual energy
- Whether the belly looks swollen or is sore to touch
- Whether it could have swallowed thread, ribbon, a sharp object or something toxic
When to book a routine visit
Any blood in stool or vomit is a reason to contact a vet the same day, even if there is only a little and your cat looks bright. If it comes with other emergency signs, go immediately.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
Body systems: Digestion and liver