# Why Is My Cat's Poop Black? Causes and When to Worry Black stool in cats usually means one of three things: digested blood from somewhere in the upper digestive tract, something in the diet or a medication, or a harmless quirk of digestion. The color alone does not tell you which one you are dealing with, so the pattern matters as much as the shade. If your cat's poop is black, the fastest way to sort out the cause is to look at the whole picture: appetite, energy, vomiting, and how long the color has lasted. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Black, tarry stool that looks like tar or coffee grounds often points to digested blood from the stomach or upper small intestine, and it needs same-day veterinary attention. - Black stool that is firm and well-formed is more often linked to diet, iron supplements, or certain medications than to bleeding. - A single dark stool in a cat that is eating, playing, and acting normal is less alarming than black stool plus vomiting, weakness, or a poor appetite. - Do not give your cat human medications, including antacids or pain relievers, without veterinary guidance. - Take a photo of the stool and note the date, then call your veterinarian. A photo helps them judge color and consistency before you arrive. ## What Black Stool Looks Like and What Is Normal Normal cat stool is brown, formed, and easy to pick up. The brown color comes from bile pigments and the normal breakdown of red blood cells as they pass through the digestive tract. Black stool is different. It can be dark brown-black, jet black, or shiny and sticky like tar. Veterinarians call this tarry appearance melena, and it usually means blood has been digested somewhere above the colon. When blood sits in the stomach or small intestine, digestive acids turn it black before it leaves the body. Some cats pass stool that looks black but is actually very dark brown. Lighting matters. A stool that looks black on a dark litter mat may look brown on a white paper towel. If you are unsure, scoop it onto a white surface and check in daylight. Consistency matters too. Hard, dry black stool is often a diet or hydration issue. Soft, sticky, tarry black stool is more concerning because it suggests blood loss. If your cat also has loose stool, read our guide to [cat diarrhea: causes, home care, and when to worry](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-diarrhea-causes-home-care) for related information. ## Main Causes of Black Stool in Cats ### Digested Blood From the Upper Gut This is the cause veterinarians worry about most. Bleeding in the stomach or upper small intestine produces black, tarry stool. Common triggers include stomach ulcers, severe gastritis, swallowed blood from a nosebleed or dental procedure, and bleeding disorders. Inflammatory bowel disease can also cause gastrointestinal bleeding. A case report described a young cat with recurring vomiting and blood in the stool who was diagnosed with lymphocytic-plasmacytic and eosinophilic enterocolitis after colonoscopy and biopsy [1]. That cat improved with prednisolone, tylosin, and metronidazole, and the medications were tapered as signs resolved [1]. This shows that chronic gut inflammation can produce bleeding that owners may notice as a color change in stool. ### Diet and Treats Some foods and treats change stool color. Diets high in certain proteins, dark-colored treats, and foods with added iron can darken stool. Blueberries, black licorice, and some charcoal-based pet products can also do it. If the color change started within a day or two of a new food, that timing is a useful clue. Switch back to the previous diet and watch the next few stools. If the color returns to normal, diet was likely the cause. If it stays black, call your veterinarian. ### Medications and Supplements Iron supplements are a classic cause of black stool. Some antibiotics and stomach medications can also darken stool. Bismuth-containing products, which are sometimes used for stomach upset, turn stool black. Never assume a medication is the cause without checking. Call your veterinarian or a pet poison hotline if you are unsure what your cat swallowed. The ASPCA Animal Poison Control Center is available at (888) 426-4435, and the Pet Poison Helpline is available at (855) 764-7661. ### Swallowed Blood Cats can swallow blood from a nosebleed, a mouth injury, a dental extraction, or a torn claw that bleeds into the mouth. The blood travels down the digestive tract and comes out black. This cause is often temporary. Once the original bleeding stops, stool color returns to normal within a few days. If black stool continues after the source has healed, something else is going on. ### Infections and Gut Inflammation Gastrointestinal infections can cause bleeding and color changes. A study of 234 cats in multicat households looked at several bacteria, including Escherichia coli, Clostridium perfringens, Clostridioides difficile, Campylobacter jejuni/coli, and Salmonella enterica, and found that diarrhea was common in that group [2]. Infection is not the same as black stool, but gut inflammation from infection can lead to bleeding. Chronic diarrhea itself has many causes, including osmotic and secretory diarrhea, impaired intestinal barrier function, and changes in intestinal motility [3]. When the gut barrier is damaged, blood can leak into the stool. If your cat has ongoing loose stool along with color changes, see our article on [cat diarrhea with mucus: causes and when to worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-diarrhea-with-mucus-causes-when-to-worry). ### Less Common Causes Rare causes include bleeding tumors, clotting disorders, and severe liver disease. Feline coronavirus can cause serious systemic disease in cats, and one report described a leopard with diarrhea and blood in the stool before a fatal outcome [4]. That case involved a wild cat, not a household pet, but it shows that viral disease can affect the gut in serious ways. | Cause | Typical clues | How urgent | |---|---|---| | Digested blood from ulcers or gastritis | Tarry, sticky black stool, vomiting, poor appetite, weakness | Emergency or same-day visit | | Diet or treats | Firm black stool, recent food change, cat acting normal | Routine visit if it persists more than 2 days | | Iron or bismuth products | Recent supplement or medication, no other signs | Call your vet to confirm | | Swallowed blood | Recent nosebleed, dental work, or mouth injury | Same-day if bleeding continues | | Gut inflammation or infection | Loose stool, mucus, weight loss, vomiting | Same-day to routine, depending on severity | | Bleeding tumor or clotting problem | Weight loss, pale gums, bruising, lethargy | Emergency | ## Red Flags That Make It an Emergency Call an emergency veterinary hospital right away if you see any of these: - Black, tarry stool plus vomiting, especially if the vomit looks like coffee grounds. - Pale or white gums. Press gently on the gum above a tooth and watch how fast the color returns. If it stays pale, that is an emergency. - Weakness, collapse, or trouble standing. - Fast breathing or a racing heart. - A swollen or painful belly. - Black stool after a known injury or after eating something sharp. - Black stool in a kitten or a cat with a long-term illness. These signs suggest significant blood loss or a serious underlying problem. Do not wait to see if it improves overnight. ## What You Can Safely Do at Home While You Wait You cannot diagnose the cause at home, but you can gather useful information and avoid making things worse. ### Take a Photo and Note the Details Photograph the stool on a white paper towel or plate. Note the date, time, and whether it was soft, firm, or tarry. Write down what your cat ate in the last 48 hours and any medications or supplements given. This information helps your veterinarian decide how urgent the situation is. ### Stop New Foods and Treats If you recently started a new food or treat, stop it and go back to the previous diet. Keep the change simple and do not add new items. Sudden diet changes can also cause diarrhea, so make any switch gradual over several days. ### Keep Your Cat Hydrated Offer fresh water in a clean bowl. Some cats drink more from a fountain. If your cat is not drinking, do not force water. Call your veterinarian instead. ### Do Not Give Human Medications Never give your cat ibuprofen, acetaminophen, aspirin, or human antacids. These can cause serious harm. Do not give any supplement for black stool unless your veterinarian prescribes it. Doses for any medication are calculated by your veterinarian based on your cat's weight and health. ### Watch the Litter Box Closely Check every stool for color and consistency. Note any straining, crying, or going outside the box. If your cat is avoiding the litter box, that can be a separate problem. See our article on [why is my cat pooping outside the litter box? causes and solutions](/knowledge/veterinary-medicine/anxiety-and-behavior-support/cat-pooping-outside-litter-box) for help with that issue. ## What Your Veterinarian Will Check and Test Your veterinarian will start with a full physical exam. They will check your cat's gums, belly, hydration, and body condition. They will ask about diet, medications, and any recent injuries. ### Common Tests - Fecal exam to look for parasites, blood, and abnormal bacteria. - Blood work to check red blood cell count, organ function, and signs of anemia. - A stool color and consistency score, which some clinics use to track changes over time [2]. - Imaging such as X-rays or ultrasound if a foreign body, tumor, or ulcer is suspected. - Endoscopy or colonoscopy in some cases. A case report described colonoscopy revealing cecal erosions that led to a biopsy diagnosis of enterocolitis in a cat [1]. ### Treatment Depends on the Cause If the cause is diet, a change back to the regular food may be enough. If the cause is an ulcer or inflammation, your veterinarian may prescribe medications such as prednisolone, tylosin, or metronidazole, as was done in one reported feline case [1]. If infection is involved, antibiotics may be needed. If blood loss is severe, a transfusion may be required. Nutritional management is a core part of long-term treatment for chronic gut problems [3]. Your veterinarian may recommend a specific therapeutic diet and a slow transition plan. ## Prevention and Monitoring You cannot prevent every cause of black stool, but you can lower the risk. - Keep your cat indoors to reduce injuries and exposure to toxins. - Feed a consistent, balanced diet and introduce new foods slowly. - Store medications and supplements out of reach. - Schedule routine wellness exams so problems are caught early. - Track your cat's litter box habits. A change in color, shape, or frequency is worth noting. - If your cat has a chronic gut condition, follow your veterinarian's monitoring plan and keep follow-up appointments. If your cat has repeated bouts of diarrhea or stool changes, keep a simple log. Note the date, color, consistency, and any other signs. This record helps your veterinarian spot patterns over time. ## Limitations and When to Contact a Veterinarian This article gives general information, not a diagnosis. Every cat is different, and only a veterinarian who examines your cat can determine the cause of black stool. Contact your veterinarian the same day if black stool lasts more than one or two stools, if your cat is eating less, or if you are unsure about the cause. Go to an emergency hospital now if you see black tarry stool with vomiting, weakness, pale gums, collapse, or a painful belly. Schedule a routine visit if the stool is firm and black but your cat is acting normal, especially if you recently changed the diet or started a supplement. ## Frequently Asked Questions ### Is black stool always a sign of bleeding? No. Black stool can come from diet, iron supplements, or bismuth products. Tarry, sticky black stool is more likely to be digested blood. Your veterinarian can test the stool for blood to tell the difference. ### Can black stool go away on its own? Sometimes. If the cause was a temporary food change or a small amount of swallowed blood, the color may return to normal within a few days. If it persists or your cat has other signs, call your veterinarian. ### What if my cat's poop is black and hard? Hard black stool often points to diet, dehydration, or constipation. It is less likely to be digested blood than tarry stool. Increase water access and talk to your veterinarian about diet and hydration. ### Should I switch my cat's food if the stool is black? Only switch if you recently started a new food and your veterinarian agrees. A sudden switch can cause diarrhea. Go back to the previous diet and watch the next few stools, then call your vet if the color does not improve. ### Can I give my cat anything at home for black stool? No. Do not give human medications or supplements. Some can make bleeding worse. Keep your cat hydrated, take a photo of the stool, and call your veterinarian for guidance. ## Related Articles - [Cat Diarrhea with Mucus: Causes and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-diarrhea-with-mucus-causes-when-to-worry) - [Why Is My Cat Pooping Outside the Litter Box? Causes and Solutions](/knowledge/veterinary-medicine/anxiety-and-behavior-support/cat-pooping-outside-litter-box) - [Cat Diarrhea: Causes, Home Care, and When to Worry](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-diarrhea-causes-home-care) - [Cat Urinating Frequently: Causes and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-urinating-frequently-causes-when-to-worry) - [Cat Vomiting and Diarrhea: When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-vomiting-diarrhea-when-to-worry) - [Cat Not Pooping but Eating Normally: Causes and When to Help](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-pooping-eating-normally) - [Dark or Black Stool in Cats: When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/dark-black-stool-cats) - [Grey Cat Poop: What the Color Means and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/grey-cat-poop-color-meaning) - [Yellow Mucus in Cat Poop: Causes and When to Worry](/knowledge/veterinary-medicine/digestive-and-urinary-care/yellow-mucus-cat-poop) ## References 1. [Case report: Lymphocytic-plasmacytic and eosinophilic enterocolitis presented with marked eosinophilia and basophilia in a cat](https://pubmed.ncbi.nlm.nih.gov/37732139/). Frontiers in veterinary science, 2023. 2. [Presence of Potential Enteropathogenic Bacteria in Cats and Association With Diarrhea in Multicat Households](https://pubmed.ncbi.nlm.nih.gov/40404601/). Journal of veterinary internal medicine, 2025. 3. [Feline chronic diarrhea: causes and nutritional management](https://pubmed.ncbi.nlm.nih.gov/42502773/). Veterinary and animal science, 2026. 4. [Molecular and pathological confirmation of natural feline coronavirus infection in a captive persian leopard (Panthera pardus tulliana): Implications for Wildlife conservation and one health](https://pubmed.ncbi.nlm.nih.gov/41200312/). Open veterinary journal, 2025. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information)