Blood in a cat's stool — whether bright red on the surface or dark and tarry — is always worth investigating, because the causes range from minor (dietary change, constipation) to potentially serious (intestinal parasites, inflammatory bowel disease, polyps, or cancer). The color and consistency of the blood tell you a great deal about where the bleeding is coming from. This article explains how to interpret what you see and when it becomes an emergency.
Last reviewed: June 2026
Red Blood vs. Dark Tarry Stool: What the Color Means
Blood in cat stool presents in two distinct ways, and understanding the difference guides urgency:
Hematochezia (bright red blood): Fresh blood coats the stool or is present in small amounts around the anus. This indicates bleeding in the lower gastrointestinal tract — the colon, rectum, or anal area. It looks alarming but is more often caused by benign problems (straining from constipation, mild colitis, anal gland issues) than by emergencies.
Melena (dark, tarry, sticky stool): Dark stool with a tar-like consistency and foul odor indicates digested blood from the upper GI tract — the stomach or small intestine. Melena is a more serious sign, associated with ulcers, intestinal tumors, coagulopathies, or foreign body damage. This warrants urgent veterinary evaluation.
A small smear of bright red blood after a single bowel movement in an otherwise active, eating cat is usually not an emergency. Recurring blood over more than 24–48 hours, blood combined with mucus, blood with lethargy or vomiting, or any melena is not a "wait and see" situation.
Common Causes by Age and Pattern
In kittens: Intestinal parasites are the most common cause. Roundworms, hookworms, coccidia, and Giardia can all cause bloody or mucoid diarrhea. A fecal examination should be done on all new kittens and kittens with GI signs.
In adult cats:
- Inflammatory bowel disease (IBD): Chronic intermittent bloody or mucoid stools with weight loss is a classic IBD presentation. Diagnosis typically requires intestinal biopsy.
- Colitis: Acute large-bowel diarrhea with red blood and straining. Often triggered by dietary indiscretion, stress, or sudden food change. Usually resolves in 2–3 days with supportive care.
- Constipation with rectal trauma: Straining to pass hard stool can rupture small rectal blood vessels.
- Polyps and tumors: Uncommon in cats but increases in likelihood with age. Colonoscopy or ultrasound may be needed.
- Anal gland problems: Impacted or abscessed anal glands can cause blood near the stool or around the anus.
In senior cats: Intestinal lymphoma (the most common GI tumor in cats), hyperthyroidism-related GI changes, and hypertensive colopathy are considerations. The AAFP-AAHA Feline Life Stage Guidelines 2021 recommend GI evaluation as part of senior wellness, especially when weight loss accompanies GI signs.
Diagnosing the Cause
A veterinary workup for blood in cat stool typically includes:
- Fecal flotation and direct smear: For parasites, protozoa, and bacteria
- Physical exam with rectal palpation
- Bloodwork (CBC + chemistry): To assess protein levels, kidney/liver function, and rule out systemic disease
- Abdominal ultrasound ($300–$600): For intestinal wall thickening, lymph nodes, masses
- GI panel (B12, folate, TLI, PLI): If malabsorption is suspected
- Colonoscopy + biopsy: Definitive for IBD vs. lymphoma
The AAFP-AAHA Feline Life Stage Guidelines 2021 note that distinguishing IBD from small cell lymphoma requires intestinal biopsy — cytology alone is insufficient. This is an important distinction because treatment and prognosis differ significantly.
Home Care for Mild, Isolated Hematochezia
If your cat had one episode of bright red blood on formed stool, is otherwise acting normally, and has no vomiting or lethargy:
- Withhold high-fat treats and rich foods for 24–48 hours
- Offer a bland diet (boiled chicken and white rice, or a GI prescription diet)
- Ensure fresh water is always available
- Monitor closely and keep the litter box clean so you can assess output
If signs resolve within 24–48 hours, schedule a routine vet visit for a fecal check. If they persist or worsen, call your vet the same day.
When to See a Vet
Call your vet today if:
- Blood in stool appears on more than one bowel movement
- Blood is accompanied by mucus, straining, or soft/liquid stool
- Your cat is also vomiting, not eating, or acting lethargic
- Your cat has lost weight over recent weeks
- Blood is dark, tarry, or has a strong foul odor (melena)
Go to the ER immediately if:
- Your cat is passing large amounts of blood with stool or without stool
- Your cat is pale, weak, cold, or collapsed
- Dark tarry stool is present alongside any signs of weakness or rapid deterioration
- Your cat is straining in the litter box and producing nothing or only blood
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Frequently Asked Questions
Is a little blood in cat poop serious? A single episode of a small smear of bright red blood on formed stool in an active, eating cat is often minor — constipation, mild colitis, or a tiny rectal vessel from straining. Two or more episodes, blood with mucus or diarrhea, or any melena (dark tarry stool) warrants a same-day vet call.
Can stress cause bloody stool in cats? Yes. Stress colitis — often called "stress-induced colitis" — causes large-bowel diarrhea with mucus and sometimes fresh blood, typically after a stressful event (moving, new pet, boarding). It usually resolves in 3–5 days. Persistent stress colitis benefits from probiotic support and veterinary assessment for IBD.
How much does it cost to diagnose blood in cat stool? A vet exam runs $50–$150. Fecal testing costs $30–$80. Bloodwork adds $100–$250. Abdominal ultrasound is $300–$600. If biopsy is needed for IBD or lymphoma, expect $500–$1,500+ for the endoscopy procedure plus pathology.
What causes a cat to have tarry, black stool? Dark tarry stool (melena) comes from digested blood, meaning bleeding is occurring in the stomach or small intestine. Causes include ulcers (from NSAIDs, stress, or underlying disease), intestinal tumors, and clotting disorders. Melena is an urgent sign — call your vet immediately or go to an emergency clinic.
Can intestinal parasites cause blood in cat stool? Yes. Hookworms (Ancylostoma species) attach to the intestinal wall and consume blood, causing bloody diarrhea and anemia. Coccidia and Tritrichomonas cause mucoid, sometimes bloody diarrhea in kittens and young cats. All new cats and kittens should have a fecal exam.
Still Not Sure if Your Cat Needs a Vet?
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