Why Does My Cat Have Blood in His Poop?

Seeing blood in your cat’s poop can be alarming, especially when it seems to come out of nowhere. As a veterinary assistant, I want you to know two things can be true at once: many causes are treatable, and some situations really do need same-day care. The key is noticing what the blood looks like, how your cat is acting, and what has changed recently.

Below is plain-English guidance for what might be going on, what you can do at home, and when it’s time to call your vet right away. This article is for education and triage, not a substitute for an exam and diagnosis.

What the blood can look like

Blood in the stool usually shows up in two common ways. Each can point to a different part of the digestive tract, but there can be exceptions.

Bright red blood

Bright red streaks or drops often suggest bleeding from the lower gastrointestinal tract, like the colon or rectum (hematochezia). In cats, this is commonly linked with constipation, irritation, colitis, parasites, or anal and rectal issues.

A quick caveat: bright red blood can also show up with severe diarrhea or rapid “transit time,” even if the irritation started higher up. If your cat has frequent watery diarrhea, treat it more seriously even if the blood is bright red.

Dark, tarry stool

Very dark, sticky, tar-like stool can indicate digested blood coming from higher up in the digestive tract (stomach or small intestine). This is called melena and is generally more urgent.

Another caveat: some foods and medications can darken stool (for example iron supplements, or bismuth-containing products like Pepto). True melena is typically black, sticky, and often has a strong, foul odor. When in doubt, call your vet.

If you are unsure which you are seeing, it is completely okay. Take a clear photo in good lighting to show your veterinarian. It helps more than you might think.

Common reasons for blood in poop

Here are common causes we see in clinics, including some that are very routine and some that need faster evaluation.

Constipation and hard stools

Hard, dry stool can create tiny tears and irritation as it passes, leading to small amounts of bright red blood. You may notice:

• Straining in the litter box
• Small, dry stool pieces
• Crying, frequent trips, or avoiding the box

If constipation or straining continues beyond a day or two, or your cat seems painful or stops eating, it is time to call your veterinarian. Chronic constipation and megacolon can occur in some cats, and early care matters.

Colitis (inflamed colon)

Colitis can cause fresh blood and mucus, often with loose stool or frequent small bowel movements. Triggers can include diet changes, stress, infections, intestinal “dysbiosis” (an imbalance of gut bacteria), or parasites.

Parasites

Intestinal parasites like roundworms, hookworms, and Giardia can irritate the gut and cause diarrhea, mucus, appetite changes, or weight changes. Blood can occur, especially when the colon is inflamed.

Even indoor cats can get parasites if they were exposed before adoption, through fleas (tapeworms), or from contaminated soil or feces tracked indoors.

Food intolerance or sudden food changes

Some cats develop digestive upset from a new food, new treats, dairy, people food, or scavenging. The gut lining can become irritated and bleed slightly. A rapid switch in diets is a frequent culprit.

(A simple distinction: an intolerance is more of an “upset stomach” response, while a true food allergy involves the immune system and often causes recurring or chronic signs.)

Hairballs and GI irritation

If a cat is grooming heavily and swallowing lots of hair, the digestive tract can get irritated. This is not a common standalone reason for blood in stool, but it may contribute, especially if your cat is also constipated or stressed.

Inflammatory bowel disease (IBD)

IBD is a chronic inflammatory condition that can cause soft stool, vomiting, appetite changes, and intermittent blood or mucus. Diagnosis often involves lab work, fecal testing, imaging, and sometimes biopsy.

Anal, rectal, or perianal irritation

While less common in cats than dogs, irritation around the anus can cause blood on the stool surface. You might see scooting, excessive licking under the tail, or sensitivity when touched. Rectal polyps or masses can also cause bright red blood and straining, especially in older cats.

Foreign material or toxins

String, ribbon, bones, certain plants, and toxic products can injure the GI tract. Some human medications (like NSAIDs) can also cause ulcers and bleeding. If you suspect ingestion, treat it as urgent.

More serious causes

• Clotting disorders
• Severe infections
• Ulcers
• Tumors or polyps (more common as cats age)

Quick checklist for your vet

These details help your veterinarian narrow the cause quickly. Jot them down (or bring a note on your phone):

• Is the blood bright red or dark and tarry?
• Is the stool formed, soft, watery, or pellet-like?
• Any mucus present?
• How often is your cat going?
• Is your cat straining (and is it poop or could it be urine)?
• Any vomiting, lethargy, weight loss, or decreased appetite?
• Any new food, treats, table food, plants, or trash access?
• Indoor-only or outdoor access?
• Current parasite prevention?
• Age and any chronic conditions (kidney disease, hyperthyroidism, etc.)?

One important note for families: straining to urinate can look like constipation. A urinary blockage is an emergency, especially in male cats. If your cat is in the box straining with little or no urine, seek emergency care.

When to call the vet today

Please seek prompt veterinary care if you notice any of the following:

• Dark, tarry stool or stool that looks like black, sticky “tar”
• Large amounts of blood (for example pooling, dripping, or more than a small streak), or bleeding that keeps happening
• Blood plus weakness, pale gums, collapse, or trouble breathing
• Repeated vomiting or cannot keep water down
• Suspected string ingestion (do not pull anything you see)
• Kittens, seniors, or cats with chronic disease showing blood in stool
• Severe diarrhea lasting more than 24 hours, or any diarrhea with dehydration signs
• Straining in the litter box with little to no urine output
• Blood in stool plus fever or obvious abdominal pain

If your cat seems “off,” trust your gut. It is always okay to call your vet and describe what you are seeing.

What you can do at home

For a cat who is acting normal, eating, and only has a small amount of bright red blood once, these steps may help while you monitor closely.

Guardrails: If blood recurs, lasts more than 24 to 48 hours, or your cat is not 100% themselves, schedule an exam. Stop home care and call your veterinarian if symptoms worsen at any point.

1) Keep things steady

Avoid rapid diet changes, new treats, and rich people foods. Keep meals simple and consistent.

2) Support hydration

• Offer fresh water in multiple locations.
• If your cat will eat it, consider adding more wet food (cats often get extra moisture this way).
• A pet water fountain can encourage drinking for some cats.

3) Reduce stress

Stress can trigger colitis in some cats. Keep the environment calm, maintain routines, and make sure the litter box is clean and easy to access.

4) Save a stool sample

Place a small fresh sample in a clean, airtight container or bag and refrigerate it (not frozen) until your appointment, ideally within 24 hours. If your clinic has specific instructions, follow those. Parasites and infections are common enough that fecal testing is often step one.

What not to do

• Do not give human medications (including Pepto, aspirin, ibuprofen, or acetaminophen). Many are dangerous for cats. Bismuth and salicylates can be especially risky.
• Do not start “leftover” antibiotics or random supplements without guidance.
• Do not delay care if your cat is lethargic, not eating, dehydrated, or producing black, tarry stool.

What your vet may recommend

Diagnosis depends on your cat’s age, symptoms, and the blood appearance. Common next steps include:

• Fecal testing for parasites and protozoa
• Physical exam including abdominal palpation and a look at the anal area when appropriate
• Bloodwork to check hydration, anemia, infection, and organ function
• Imaging (x-rays or ultrasound) if a foreign body, constipation, mass, or thickened intestines are suspected
• Deworming even if parasites are not seen, depending on risk factors
• Diet trial (novel protein or hydrolyzed diet) if food sensitivity or IBD is suspected
• Probiotics designed for cats, if appropriate

Most importantly, your veterinarian will match treatment to the cause. That is why a quick exam and fecal test can save a lot of worry and trial and error at home.

Prevention tips

• Parasite prevention: keep your cat on vet-recommended flea and parasite control, especially if there is any outdoor exposure.
• Slow food transitions: mix new food into old food over 7 to 10 days when possible.
• Hairball support: regular grooming and vet-approved hairball strategies can reduce GI irritation.
• Hydration-first feeding: many cats do better with some wet food for moisture support.
• Routine vet visits: early changes in weight, appetite, and stool patterns are easier to address.

If you have kids at home, this is also a great chance to teach a gentle “health detective” habit: notice eating, drinking, energy, and litter box patterns. It is one of the simplest ways families can help pets stay healthy.

Bottom line

A small streak of bright red blood in an otherwise normal cat can be caused by something as common as constipation or mild colitis. But dark, tarry stool, repeated bleeding, a lot of blood, or any signs your cat feels unwell deserve prompt veterinary attention. If you are in doubt, call your vet and describe the color and amount of blood, your cat’s energy level, and what the poop looks like. Those details are incredibly helpful.