Blood in Cat Stool: What It Means and What to Do

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Blood in the litter box is alarming in a way that most cat health signs are not, and the alarm is not always proportionate to the danger. A few red streaks on an otherwise normal stool from a cat who is eating and playing normally is a different situation from black tarry stool in a cat who has gone quiet.

The distinction that matters is colour, because colour tells you roughly where the bleeding is coming from. This guide covers the two forms of blood in stool, what causes each, how urgently to act, and what your vet will want to know when you call.

The two kinds of blood

Veterinary practice separates blood in stool by colour, because colour is a rough proxy for how far the blood travelled through the gut before it left.

Bright red, hematochezia

Fresh red blood has not passed through the digestive process. It entered the stool late, in the colon or rectum, and arrives looking like blood.

It usually appears as streaks on the surface of a formed stool, as spots in the litter, or mixed through loose stool with jelly-like mucus.

The territory it points to includes colitis, straining from constipation, anal gland problems, polyps, parasites and dietary upset.

Black and tarry, melena

Blood that entered high in the digestive tract gets broken down on the way through, and what arrives is black, sticky and tar-textured rather than red.

Melena points to bleeding in the oesophagus, stomach or small intestine. The causes include ulcers, foreign bodies, tumours and clotting disorders.

Melena is the more serious of the two findings, and it warrants a same-day veterinary visit rather than a phone call.

UNIQUE INSIGHT

There is a practical problem with spotting melena that almost no article mentions, and it is worth knowing because it is the reason melena gets missed in cats far more often than in dogs. Melena is dark, and so is used clumping clay litter, walnut shell litter and anything else that has been sitting in a box. Black stool against dark litter, under a hood, at the end of a scoop, is close to invisible. Two habits fix it. Scoop in good light and actually look, rather than scooping by feel. And if you are already watching a cat for a gut problem, consider a lighter-coloured litter for the duration, because the contrast is the entire diagnostic. Walnut litter is the worst offender here, and it is a genuine reason to switch temporarily even though it performs well otherwise.

How urgent is it?

That last row deserves emphasis. A cat straining in the box producing blood-tinged drops may not have a gut problem at all. Blood-tinged urine with straining and little output can indicate a urinary blockage, which Cornell notes can kill within less than twenty-four to forty-eight hours. If you cannot tell whether the blood is in stool or urine, treat it as urinary and go.

What causes it

Parasites

Common, and a leading cause in kittens and cats with outdoor access. Worms and protozoal parasites both irritate the gut lining. Visible worms in stool, whether rice-like tapeworm segments or spaghetti-like roundworms, point straight here.

Colitis

Inflammation of the colon, producing loose stool with mucus and fresh red blood, often with more frequent trips to the box and urgency. Causes range from dietary change and stress to inflammatory bowel disease.

Constipation

Hard, dry stool can tear the delicate lining on the way out, producing a small amount of bright red blood on the surface of an otherwise firm stool. Cornell defines constipation as "infrequent or difficult emission of hard, dry fecal matter" and notes it requires aggressive intervention, so treat the constipation rather than dismissing the blood.

Dietary change and food intolerance

An abrupt food switch is a common trigger for colitis-type signs. Transition food over seven to ten days.

Anal gland problems

Impacted or infected anal glands can produce blood and discomfort, often with excessive licking or scooting.

Foreign bodies

Anything swallowed that should not have been. String is the dangerous version: if you see string protruding from your cat's rectum, do not pull it, go to an emergency vet.

Inflammatory bowel disease and lymphoma

Both present with chronic gut signs in cats, and both are more common in older animals. Persistent or recurring blood needs a proper workup rather than repeated short-term fixes.

Clotting disorders and toxins

Less common, and serious. Some rodenticides interfere with clotting and can cause bleeding into the gut.

What your vet will want to know

Calling with good information saves time and sometimes a second visit.

How much blood, and how often. Once, or every stool for three days?

Red or black. Say which, plainly. If you are unsure, say that too.

Stool consistency, ideally as a score on the 7-point scale, where 1 is hard dry pellets and 7 is watery.

Whether your cat is eating, drinking, playing and behaving normally.

Any vomiting, weight loss or lethargy.

Recent changes: new food, new treats, a house move, a new pet, medication, or access to plants and chemicals.

Whether other pets in the house are affected.

Parasite prevention status and when it was last given.

Bring evidence

A fresh stool sample in a sealed bag, collected within a few hours, lets your vet run a faecal test at the visit rather than asking you to come back.

A photograph taken in natural light is the next best thing, and it is far more useful than a verbal description of a colour. Take it before you scoop.

Keep a short log if the problem is recurring: date, consistency score, whether blood was present, and what the cat ate. Patterns that are invisible day to day become obvious across two weeks.

What not to do

Do not give human anti-diarrhoeal medication. Cornell warns directly that "some over the counter medications can be harmful to cats."

Do not withhold water. Cats with gut problems lose fluid, and cats dehydrate faster than owners expect.

Do not change food abruptly in response, since an abrupt change is itself a common trigger.

Do not wait to see if black tarry stool resolves on its own.

Do not pull anything protruding from your cat's rectum.

Frequently Asked Questions

Is blood in cat stool always an emergency?

No, and it always warrants a vet conversation. A few bright red streaks on a formed stool in a cat that is otherwise well is usually a call-today situation. Black tarry stool, large volumes of blood, or blood in a cat that is lethargic, vomiting or off its food needs to be seen the same day.

What does black tarry cat poop mean?

It is melena, which is digested blood from the upper digestive tract, pointing to bleeding in the oesophagus, stomach or small intestine. It is the more serious of the two presentations and needs a same-day visit.

What does bright red blood in cat poop mean?

It is hematochezia, fresh blood from the colon or rectum. Common causes include colitis, straining from constipation, parasites and anal gland problems.

My cat has blood in stool but seems fine. Should I still call?

Yes. Cats hide illness well, and normal behaviour does not rule out a condition that needs treating. A single episode in a well cat is a call rather than an emergency, but it should not be ignored.

Could it be constipation?

Yes. Hard, dry stool can tear the lining on the way out and leave bright red blood on the surface. The blood is a consequence of the constipation, so the constipation is what needs treating.

Can stress cause blood in cat stool?

Stress is a recognised contributor to colitis in cats, and Cornell lists stress among the causes of feline diarrhoea. It is worth mentioning any household change when you call, and it should not be assumed as the cause without a vet ruling out the others.

Should I change my cat's food?

Not without veterinary advice, and not abruptly. An abrupt change is itself a common trigger for gut upset.

How do I collect a stool sample?

Scoop the freshest sample you can into a clean sealed bag or a container, keep it cool, and bring it within a few hours. Litter stuck to the outside is not a problem.

SOURCES & CITATIONS

Cornell University College of Veterinary Medicine, Cornell Feline Health Center "Diarrhea," retrieved 2026-09-02 https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/diarrhea

Cornell University College of Veterinary Medicine, Cornell Feline Health Center "Constipation," retrieved 2026-09-02 https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/constipation

Cornell University College of Veterinary Medicine, Cornell Feline Health Center "Feline Lower Urinary Tract Disease," retrieved 2026-09-02 https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-lower-urinary-tract-disease

Purina Fecal Scoring Chart 7-point veterinary scale, retrieved 2026-09-02