Blood in cat poop doesn’t always look the way you’d expect. It can range from bright red streaks on the surface of formed stool to a black, tar-like consistency throughout, and each appearance points to a different part of the digestive tract. Knowing what to look for helps you give your vet useful information fast.
Bright Red Blood
The most recognizable form is bright red blood, either streaked on the outside of the stool, mixed into diarrhea, or visible on the fur around your cat’s anus. This color means the bleeding is happening near the end of the digestive tract: the large intestine, rectum, or anal area. Because the blood hasn’t had time to be digested, it keeps its fresh red color.
You might see just a few drops or spots on the surface, or the entire stool might have a reddish tinge. In more significant cases, the blood can pool enough to form small, dark red, gelatin-like clots within the poop. If you notice red blood only on the outside of otherwise normal-looking stool, that often points to an issue right at the rectum or anus, like irritated anal glands or a small tear.
Black, Tarry Stool
When bleeding starts higher up in the digestive system (the stomach, esophagus, or small intestine), the blood gets partially digested before it reaches the litter box. The result is stool that looks black and sticky, almost like tar. This form, called melena, can be easy to miss if your cat uses dark-colored litter.
Black stool is generally more concerning than bright red blood because it signals a problem further up the GI tract, where conditions like ulcers or tumors may be involved. Neoplasia, particularly certain types of intestinal tumors, is a recognized risk factor for upper GI ulcers and bleeding in cats. If your cat’s stool suddenly turns uniformly dark and has a distinctly foul or metallic smell, that warrants prompt veterinary attention.
Mucus With Blood
Sometimes you’ll notice a jelly-like mucus coating the stool alongside streaks of blood. This combination typically points to inflammation in the large intestine, a condition called colitis. The colon produces extra mucus when its lining is irritated, so seeing both mucus and fresh blood together is a hallmark sign.
Colitis in cats can be triggered by stress, food allergies or intolerances, parasites, or infections. It often comes with softer stools, increased urgency, or straining in the litter box. A single episode after a stressful event (a move, a new pet in the house) may resolve on its own, but repeated episodes need investigation.
Common Causes of Bloody Stool
The list of possible triggers is broad, but a few show up far more often than others:
- Parasites. Hookworms attach to the intestinal wall and feed directly on blood. Severe hookworm infections can cause black, tarry stool from blood loss and even anemia. Coccidia, a microscopic single-celled parasite, can destroy the intestinal lining in kittens and cause mucus-filled, bloody diarrhea. Roundworms and other intestinal worms can also produce bloody or mucousy feces.
- Food allergies or dietary indiscretion. Eating something that irritates the gut, or a reaction to a specific protein in food, can inflame the colon enough to cause bleeding.
- Colitis. Inflammation of the large intestine from stress, infection, or food intolerance is one of the most frequent culprits behind bright red blood in cat stool.
- Anal gland problems. Impacted or infected anal glands can produce blood that appears on the stool’s surface or around the anus.
- Medication reactions. Certain medications, particularly anti-inflammatory drugs, can irritate the stomach lining and lead to bleeding.
Signs That Need Immediate Attention
A single small streak of red blood on an otherwise normal stool isn’t always an emergency, but certain patterns are. If your cat has severe bloody diarrhea, especially with vomiting, weakness, or collapse, that combination can indicate rapid blood loss or a serious infection requiring same-day veterinary care. Lethargy, pale gums, loss of appetite lasting more than a day, or bloody stool that persists beyond 12 hours are all reasons to call your vet rather than wait and see.
Black, tarry stool at any volume deserves a prompt call. Because the bleeding source is higher in the digestive tract, the underlying cause tends to be more serious, and the amount of blood lost may be greater than it appears.
What Your Vet Will Want to See
Bringing a stool sample to your appointment saves time and often saves your cat from extra stress. Collect a piece about one inch long, as clean as possible (minimal litter stuck to it), and place it in a sealed plastic bag or small jar. If your appointment is within six hours, room temperature is fine. If it will be longer than that, refrigerate the sample, but don’t use it if it’s been sitting unrefrigerated for more than six hours, since accuracy drops quickly.
Your vet can run a fecal test to check for parasites, bacteria, and other pathogens. In some cases, they may also use an occult blood test to detect hidden blood that isn’t visible to the naked eye. If the cause isn’t obvious from a stool test and basic bloodwork, the next steps might include an abdominal ultrasound or a scope of the upper or lower GI tract to look at the intestinal lining directly.
How to Spot It in the Litter Box
Clumping litter can mask blood, especially the dark, tarry kind. If you suspect something is off, try switching temporarily to a lighter-colored, non-clumping litter so any discoloration is easier to see. Check the stool before your cat buries it if possible. Look at the surface first for streaks or spots, then break it open with a disposable utensil to check inside. Fresh blood on the outside with a normal brown interior suggests a lower-tract source. A uniformly dark or reddish color throughout suggests the blood has been mixed in higher up.
Taking a photo with your phone before cleaning the box gives your vet a useful visual reference, especially if the appearance changes between episodes.