Why Is My Cat Pooping Blood? 5 Causes & When to Worry

Blood in your cat's stool is most often caused by something manageable — dietary upset, intestinal parasites, or stress-related colitis — but any amount of blood is worth a vet's attention, especially if it happens more than once or comes with other symptoms.

Common Causes of Blood in Cat Stool

Intestinal parasites and colitis (inflammation of the colon) are two of the most frequent reasons cats pass blood in their stool, and both are very treatable once identified.

A veterinarian who reviews this exact symptom regularly explained the colitis connection directly:

"Inflammation of the large intestine, or colitis, can cause your cat to start pooping blood." — Dr. Paola Cuevas, MVZ at Catster

Parasites are just as common a culprit, and the right treatment depends entirely on which one is involved:

"Gastric parasites can also cause your cat to start pooping blood. The treatment varies based on the parasite your cat hosts, just like with infections." — Dr. Paola Cuevas, MVZ at Catster

A fecal test at the vet is the standard way to identify which parasite (if any) is involved, since treatment differs significantly between, say, roundworms and giardia.

Diet, Stress, and Digestive Sensitivity

A sudden food change, a new treat, or even a stressful event at home can upset a cat's digestive tract enough to cause loose stool with streaks of blood, without any underlying disease being involved.

This is especially common after switching cat foods too quickly, or if a cat has eaten something outside its normal diet. Cats with an ongoing sensitive stomach often do better on a simpler, more consistent diet:

If you suspect diet is the trigger, transitioning to any new food gradually over 7 to 10 days (mixing increasing amounts of the new food with the old) reduces digestive upset considerably compared to switching all at once.

When Blood in Cat Stool Is an Emergency

Bright red blood mixed with diarrhea, large amounts of blood, or blood alongside vomiting, lethargy, or refusal to eat are all signs that need same-day veterinary attention rather than a wait-and-see approach.

A veterinarian who reviews pet health content put it plainly:

"Even if your cat seems fine, blood in the stool should never be ignored. It may be the first sign of illness, and early evaluation can make a big difference in treatment." — Dr. Joana Babo, DVM at Maven Pet

This matters even when a cat otherwise seems totally normal — bright, alert, eating, and playing as usual. Blood in the stool can be the very first visible sign of a problem, well before a cat shows any other symptom of feeling unwell.

What to Do Right Now

A single small streak of blood in an otherwise healthy, normal-acting cat is reasonable to monitor for a day, but a vet visit is the right call if it happens again, gets worse, or shows up with any other symptom.

Bring a stool sample with you if you can manage it — even a small amount collected in a clean bag or container speeds up diagnosis significantly, since many of the most common causes (parasites especially) are identified directly from a fecal test.

Also Read: Pet first-aid and digestive care essentials many cat owners keep on hand

In Short

Blood in cat stool is most often caused by parasites, colitis, or a diet/stress-related digestive upset — all manageable once identified. A single mild instance in a cat that otherwise seems fine is reasonable to monitor briefly, but recurring blood, large amounts, or blood alongside vomiting or lethargy needs same-day veterinary care. Bringing a stool sample to the vet visit speeds up diagnosis considerably.

What You Also May Want To Know

Is a little blood in my cat's stool an emergency?

Not always. A single small streak in a cat that otherwise seems normal is reasonable to monitor for a day. Recurring blood, large amounts, or blood alongside vomiting, lethargy, or appetite loss needs same-day veterinary attention.

What does it mean if my cat has bright red blood versus dark blood in its stool?

Bright red blood usually points to a source lower in the digestive tract, like the colon or rectum (common with colitis). Darker, tarry-looking stool can indicate bleeding higher up in the digestive tract and is generally taken more seriously.

Can a diet change really cause blood in my cat's stool?

Yes. Switching foods too quickly, or a cat eating something outside its normal diet, can upset the digestive tract enough to cause loose stool with streaks of blood, even without any underlying disease.

Should I bring a stool sample to the vet?

Yes, if you can manage it. A fresh stool sample speeds up diagnosis significantly, since many common causes, especially parasites, are identified directly from a fecal test.

Can stress alone cause my cat to poop blood?

Yes, stress-related colitis is a real and fairly common cause, especially after a household change like moving, a new pet, or a disruption to routine. It's still worth a vet visit to rule out other causes first.

Reviewed and Updated on June 25, 2026 by George Wright