Blood in a cat’s stool usually signals irritation or injury somewhere along the digestive tract. The location and severity range from minor (a slightly inflamed colon) to serious (internal bleeding or a severe infection), so the appearance of the blood itself is your first clue about what’s going on.
Bright red blood means the problem is in the lower digestive tract, typically the colon or rectum. Dark, tarry, almost black stool points to bleeding higher up, in the stomach or small intestine, where blood has been partially digested before passing through. Both warrant attention, but dark tarry stool generally indicates more acute or significant blood loss.
Colitis and Inflammatory Bowel Disease
One of the most common reasons cats bleed when they poop is colitis, which is inflammation of the large intestine. When the colon’s lining becomes irritated and swollen, it bleeds easily as stool passes through. You’ll typically see bright red blood mixed with mucus, and your cat may strain visibly in the litter box or make frequent trips without producing much.
Colitis can be a short-term problem triggered by stress, a dietary change, or a mild infection. But in some cats it becomes chronic, falling under the broader category of inflammatory bowel disease (IBD). In feline IBD, the immune system mounts an overly aggressive response to normal gut bacteria, sending waves of inflammatory cells into the intestinal walls. Over time, this thickens the tissue, disrupts nutrient absorption, and creates a fragile mucosal surface prone to erosions and bleeding. Cats with IBD often have intermittent diarrhea with blood, weight loss, and a dull coat that doesn’t improve on its own.
Intestinal Parasites
Parasites are a leading cause of bloody stool, especially in kittens and outdoor cats. Prevalence rates run as high as 45% in some cat populations, according to Cornell University’s College of Veterinary Medicine.
Hookworms are particularly notable because they physically attach to the intestinal wall and feed on blood. A mild infection might cause diarrhea and weight loss, but a heavy hookworm burden can cause enough blood loss to make a cat anemic. In severe cases, the stool turns black and tarry from digested blood.
Coccidia, a single-celled parasite, is another common culprit. Nearly all cats encounter coccidia at some point in their lives. Adults usually fight it off without symptoms, but in kittens, these organisms can destroy the intestinal lining and produce mucus-filled, bloody diarrhea. Giardia infections are less common (under 5% of cats) and more often cause watery diarrhea than overt bleeding, though they can still contribute to intestinal irritation.
Food Allergies and Dietary Triggers
Food allergies in cats most commonly show up as skin problems, but an estimated 10 to 15 percent of allergic cats also develop gastrointestinal symptoms like vomiting, diarrhea, and bloody stool. The immune reaction targets proteins in the diet (often chicken, beef, fish, or dairy), causing chronic low-grade inflammation in the gut. Cats with food-related GI issues may also start avoiding meals, leading to weight loss that compounds the problem.
Even without a true allergy, a sudden switch in food, spoiled food, or ingredients a cat isn’t used to can inflame the colon enough to produce a streak of blood. This type of dietary upset usually resolves within a day or two once the trigger is removed.
Anal Gland Problems
Sometimes the blood isn’t actually coming from inside the digestive tract at all. Cats have two small anal sacs on either side of the anus that normally release a small amount of fluid each time they defecate. When these sacs become impacted or infected, the fluid turns bloody. Eventually, the buildup can form an abscess that drains pus and blood from the anus, making it look like the blood is in the stool.
Signs of anal gland trouble include scooting, excessive licking around the rear end, and visible swelling or redness near the anus. Infections can occasionally develop without impaction, with bloody discharge draining through the duct and appearing on the surface of the stool or in the litter box.
More Serious Causes
Intestinal tumors, particularly lymphoma (the most common GI cancer in cats), can cause chronic bleeding as growths ulcerate the intestinal wall. This is more typical in older cats, and the bleeding often accompanies progressive weight loss, decreased appetite, and vomiting.
Ingesting something toxic or a foreign object can also tear or irritate the GI lining. Cats that chew on string, rubber bands, or small toys risk linear foreign bodies that can saw through intestinal tissue, causing significant internal bleeding. Certain household toxins, including some plants and human medications like ibuprofen, can cause stomach ulcers and bloody stool.
What the Color and Pattern Tell You
A single episode of a small streak of bright red blood on otherwise normal stool is the least concerning scenario. It often points to minor irritation in the colon or a hard stool that scratched the rectal lining on its way out.
Repeated bright red blood, especially with diarrhea, mucus, or straining, suggests ongoing inflammation from colitis, parasites, or an allergy. Dark, tar-like stool is more urgent. True melena (the clinical term for this) only appears when a significant amount of blood enters the upper GI tract. It looks pitch black, almost like asphalt, and has a distinctive foul smell.
Any bloody stool paired with lethargy, repeated vomiting, loss of appetite, pale gums, or sudden weakness is a situation that needs same-day veterinary attention. Pale gums in particular indicate blood loss significant enough to cause anemia, and sudden collapse can signal internal bleeding or a heart-related emergency.
How Vets Find the Cause
A vet will typically start with a fecal exam, using a flotation test to check for parasite eggs under a microscope. This is quick, inexpensive, and catches most common worms and coccidia. Some clinics also run PCR panels that detect parasite DNA, which is more sensitive for organisms like Giardia that don’t always show up on standard tests.
If parasites are ruled out, the next steps usually include blood work to check for anemia, organ function, and markers of inflammation. An abdominal ultrasound can reveal thickened intestinal walls (a hallmark of IBD), masses, or foreign objects. For suspected IBD, a definitive diagnosis requires intestinal biopsies, typically collected through endoscopy, which allows the vet to see mucosal damage directly and count the inflammatory cells in tissue samples.
For suspected food allergies, the gold standard is an elimination diet trial. Your cat eats a single novel protein or hydrolyzed protein diet for 8 to 12 weeks while all other foods and treats are removed. If symptoms resolve and return when the old food is reintroduced, the allergy is confirmed.
Treatment Depends on the Cause
Parasite infections are usually straightforward to treat with deworming medication, sometimes requiring a second dose a few weeks later to catch newly hatched larvae. Kittens with heavy coccidia infections may need supportive care and fluids if they’ve become dehydrated from diarrhea.
Colitis from dietary indiscretion or stress often resolves with a temporary switch to a bland or easily digestible diet, sometimes supplemented with fiber to normalize stool consistency. Probiotics may help restore healthy gut bacteria after a bout of inflammation.
IBD requires longer-term management. Treatment typically involves dietary modification combined with medications that suppress the overactive immune response in the gut wall. Many cats with IBD go through periods of remission and flare-ups, and finding the right combination of diet and medication can take some trial and adjustment. Cats with IBD whose symptoms include bloody stool from colonic inflammation tend to respond well once the right approach is identified, though they often need ongoing monitoring.
Anal gland infections are treated by expressing the impacted material and clearing the infection with antibiotics. Abscesses that have ruptured need to be flushed and may require a short course of pain medication during healing.