# Blood Clots in Cats: Leg, Bladder, and Eye Symptoms Blood clot in cats symptoms usually appear suddenly and are severely painful. A clot that blocks blood flow to a leg causes paralysis and crying, while clots in the bladder or eye cause blood in the urine or a cloudy, painful eye. Minutes matter in every case. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Sudden hind leg paralysis, dragging, cold limbs, and loud crying are the classic signs of a clot blocking blood flow to the legs [1]. - A blood clot in cats urine often shows up as blood in the urine or straining to urinate, and it needs same-day veterinary care. - A blood clot in cats eye can cause a sudden cloudy, red, or painful eye, sometimes with vision loss. - Cats with heart disease, especially cardiomyopathy, are at the highest risk because clots form in the heart and travel through the bloodstream [1]. - If your cat cannot use a leg, is screaming in pain, or is struggling to breathe, call your veterinarian or an emergency hospital right now and start driving. ## What a Clot Looks Like and What Is Normal A blood clot is a clump of blood that forms where it should not. It can block an artery or a vein at the spot where it forms, or it can break loose and travel until it lodges somewhere narrower [2]. When that happens, tissues past the blockage stop getting blood, and they start to die. Cats hide pain well, so the first sign is often dramatic instead of subtle. A normal cat stretches, jumps, and walks without complaint. A cat with a clot in a leg may suddenly stop using that leg, drag it, or hold it stiff and low. Many cats cry out, pant, or growl when the leg is touched because the pain is intense [1]. Normal urine is clear to yellow, with no visible blood and no long straining. Normal eyes are bright and clear, with no sudden color change or squinting. Any abrupt change in these areas deserves a call to your veterinarian. ## Main Causes of Blood Clots in Cats Clots do not appear out of nowhere. Most feline clots trace back to the heart, to a damaged blood vessel, or to a condition that makes the blood clot too easily [2]. Cats with cardiomyopathy, a disease of the heart muscle, often form clots in major arteries because of damage to the heart wall and abnormal blood flow [1]. The left atrium can enlarge, and clots can form inside it. Part or all of a clot can then break off and travel as an embolus until it lodges in a narrower vessel [2]. | Cause | Typical clues | How urgent | |---|---|---| | Heart disease (cardiomyopathy) with arterial thromboembolism | Sudden hind leg paralysis, cold limb, severe pain, often a heart murmur or arrhythmia | Emergency now | | Clot in the bladder or urinary tract | Blood in the urine, straining, frequent small urinations, sometimes a partial blockage | Same day, emergency if the cat cannot pass urine | | Clot in or near the eye | Sudden cloudy, red, or painful eye, squinting, vision changes | Same day | | Disseminated intravascular coagulation (DIC) | Many tiny clots throughout the body, which use up platelets and clotting factors and cause uncontrollable bleeding and organ failure [1] | Emergency now | | Aneurysm with clot formation | Rare in cats, caused by weakening of the middle layer of a blood vessel [2] | Emergency now | Some cats with heart disease caused by hyperthyroidism may be given medications that lower clot risk by changing platelet activity [1]. Your veterinarian chooses the treatment, including blood thinners, based on your cat's specific condition [1]. ## Blood Clot in Cats Leg or Hind Legs This is the most common and most frightening presentation. A clot that blocks blood flow to a leg causes sudden pain and paralysis [1]. Owners often describe a cat that was fine an hour ago and now cannot stand on one or both back legs. ### What you will see - The affected leg or legs are limp, stiff, or dragged. - The paw and lower leg feel cool to the touch compared with the other side. - The cat cries, pants, or growls, especially when the leg is handled. - The cat may be unable to walk, or may walk on the front legs only. - The pads may look pale or bluish. ### Why it is so painful When an artery is blocked, the muscles and nerves past the blockage are starved of blood and oxygen. That ischemia is what drives the intense pain. In one reported case, a 12-year-old cat with a clot in the aorta improved at first with antithrombotic therapy, narcotic analgesia, and a diuretic, then suddenly deteriorated when bacteria in the oxygen-starved limb caused gas gangrene [3]. That case report proposed giving benzyl penicillin intravenously to cats with this type of clot as bacterial prophylaxis, though this is not yet standard for every cat [3]. ## Blood Clot in Cats Urine or Bladder A blood clot in cats urine is a different problem from a leg clot, but it still needs prompt care. Blood in the urine can come from a clot, from inflammation, from infection, or from bladder stones. You cannot tell which one it is at home. Watch for pink, red, or brown tinge in the urine, straining that produces only drops, licking at the belly or genital area, and urinating outside the box. These signs overlap with common urinary problems, so it helps to read more about [Symptoms Of Bladder Infection In Cats](/knowledge/veterinary-medicine/symptom-guides/symptoms-of-bladder-infection-in-cats) and [Cat Blood in Urine: Causes and When to Rush to the Vet](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-blood-in-urine-causes-when-to-rush). A clot can also physically block the urethra. If your cat is straining and nothing comes out, or if the cat is crying and pacing, that is a life-threatening blockage and an emergency. For a closer look at the difference between a mild episode and a true crisis, see [Cat Blood in Urine but Acting Normal: Causes and Next Steps](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-blood-urine-acting-normal). ## Blood Clot in Cats Eye A clot in the blood vessels feeding the eye can cause sudden vision loss, a cloudy or bluish cornea, a red or blood-filled eye, or a pupil that looks different from the other side. The eye may be painful, and the cat may squint, paw at the face, or bump into furniture. Eye clots are less common than leg clots, but they can be the first sign of underlying heart disease or high blood pressure. Any sudden change in one or both eyes should be examined the same day. Do not wait to see if it clears up on its own. ## Red Flags That Make It an Emergency Call an emergency hospital immediately if you see any of these: - Sudden paralysis or weakness in one or both hind legs. - Loud crying, panting, or growling that suggests severe pain. - A limb that feels cold or looks pale or blue. - Straining to urinate with no urine produced. - Blood in the urine along with vomiting, lethargy, or not eating. - Sudden cloudy, red, or painful eye, especially with wobbling or head tilt. - Open-mouth breathing, collapse, or a racing heart. A clot in a leg is a minutes-matter emergency. The longer the tissue goes without blood, the more damage occurs, and the more likely the cat will need intensive care or euthanasia. ## Safe Things You Can Do at Home While Waiting There is no home treatment for a clot. Your job is to keep your cat calm and get to the veterinarian. - Do not massage or stretch the affected leg. Handling it increases pain and will not break up the clot. - Do not give any human pain medication. Many are toxic to cats, and the dose must be calculated by a veterinarian based on your cat's weight and health. - Do not give aspirin or any blood thinner unless your veterinarian has prescribed it for this cat. - Wrap your cat in a towel or place it in a carrier with a soft pad. Keep the car warm. - Call ahead so the clinic can prepare for a cat in severe pain. - If your cat is struggling to breathe, keep the carrier open and the car cool, and drive directly to the nearest emergency hospital. ## What Your Veterinarian Will Check and Test Your veterinarian will start with a physical exam. They will check the affected leg for pulse, temperature, and color, listen to the heart for a murmur or arrhythmia, and check the eyes and gums. Testing may include: - Blood work to look for organ problems, infection, and clotting abnormalities. - Echocardiography (heart ultrasound) to look for an enlarged left atrium, a clot inside the heart, or heart muscle disease [4]. - Doppler ultrasound to check blood flow in the affected limb or eye. In one reported case, Doppler confirmed absent blood flow in the affected tongue region when a clot was suspected there [4]. - Platelet function testing, which is used in the diagnosis and management of bleeding and clotting disorders in cats [5]. - Global hemostatic tests such as thromboelastography and thrombin generation testing, which researchers have used to evaluate the clotting state of cats with cardiomyopathy and clots [6]. Treatment depends on the site and severity. It may include pain control, oxygen, blood thinners, and supportive care. In one reported case, a cat with a suspected clot in the tongue artery was treated with anticoagulant therapy and supportive care, but worsening tongue swelling and functional impairment affected the outcome [4]. Your veterinarian will explain what is realistic for your cat. ## Prevention and Monitoring If your cat has heart disease, the goal is to lower clot risk before a clot happens. Your veterinarian may prescribe medications that change platelet activity or thin the blood, and the choice depends on your cat's condition [1]. Keep every recheck appointment. Heart changes can progress quietly, and an exam plus ultrasound can catch an enlarging atrium before a clot forms. Ask your veterinarian whether your cat should be screened for hyperthyroidism, since heart disease caused by hyperthyroidism can be managed in part with medications that lower clot risk [1]. At home, watch for subtle changes: a new reluctance to jump, faster breathing at rest, or hiding more than usual. Keep your emergency clinic's address and phone number on your refrigerator. If your cat has had a clot before, ask your veterinarian for a written plan that says exactly where to go and what to do if signs return. ## Limitations and When to Contact a Veterinarian This article cannot tell you whether your cat has a clot. Only a veterinarian can examine your cat, check blood flow, and run the right tests. Contact your veterinarian the same day for blood in the urine, a sudden cloudy or red eye, or any new limping that does not improve within a few hours. Go to an emergency hospital now for sudden hind leg paralysis, a cold limb, severe crying or panting, straining to urinate with no urine, open-mouth breathing, or collapse. Schedule a routine visit for monitoring if your cat has known heart disease but is stable, or if your veterinarian has asked you to recheck platelet or clotting tests. Individual cases need a veterinarian who can examine your cat in person. ## Frequently Asked Questions ### Can a blood clot in a cat's leg heal on its own? Sometimes a partial clot allows some blood flow to return, but you cannot predict this at home. The pain is severe, and permanent nerve and muscle damage can happen within hours. Any cat that suddenly cannot use a leg needs emergency care right away. ### How do I know if blood in my cat's urine is from a clot? You cannot tell from looking at it. Blood in the urine can come from a clot, an infection, inflammation, or bladder stones, and the treatment is different for each. Your veterinarian can test the urine and, if needed, use imaging to find the source. ### Is a cloudy eye in a cat always a clot? No. Cloudy eyes have many causes, including injury, high pressure inside the eye, and inflammation. A clot is one possibility, especially in a cat with known heart disease. Because a sudden eye change can threaten vision, have it examined the same day. ### Are some cats more likely to form clots? Yes. Cats with heart muscle disease, especially with an enlarged left atrium, are at higher risk because clots can form in the heart and travel through the bloodstream [2][1]. Cats with hyperthyroidism-related heart disease also have added risk, which is one reason thyroid screening matters [1]. ### What tests show that a cat is forming clots too easily? Veterinarians may use platelet function testing, which is a key part of diagnosing and managing clotting disorders in cats [5]. They may also use global hemostatic tests such as thromboelastography and thrombin generation testing, which have been studied in cats with cardiomyopathy and arterial thromboembolism [6]. Your veterinarian will choose the tests that fit your cat's signs and history. ## Related Articles - [Symptoms Of Bladder Infection In Cats](/knowledge/veterinary-medicine/symptom-guides/symptoms-of-bladder-infection-in-cats) - [Cat Blood in Urine but Acting Normal: Causes and Next Steps](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-blood-urine-acting-normal) - [Why Is My Cat having blood in urine? UTI and Bladder Stones Diagnosis](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-having-blood-in-urine-uti-and-bladder-stones-diagnosis) - [Cat Blood in Urine: Causes and When to Rush to the Vet](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-blood-in-urine-causes-when-to-rush) - [Symptoms Of Urinary Infection Cats](/knowledge/veterinary-medicine/symptom-guides/symptoms-of-urinary-infection-cats) - [Cat Urinary Infection Symptoms](/knowledge/veterinary-medicine/symptom-guides/cat-urinary-infection-symptoms) ## References 1. [Bleeding and Clotting Disorders in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/blood-disorders-of-cats/bleeding-and-clotting-disorders-in-cats). Merck Veterinary Manual. 2. [Blood Clots and Aneurysms in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/heart-and-blood-vessel-disorders-of-cats/blood-clots-and-aneurysms-in-cats). Merck Veterinary Manual. 3. [Gas gangrene due to Clostridium haemolyticum in a cat with aortic thromboembolism treated using clopidogrel and rivaroxaban](https://pubmed.ncbi.nlm.nih.gov/39739656/). Australian veterinary journal, 2025. 4. [Tongue infarction in suspected lingual artery thromboembolism in a cat with hypertrophic cardiomyopathy](https://pubmed.ncbi.nlm.nih.gov/41978704/). JFMS open reports, 2026. 5. [Optimization of conditions related to Chrono-log platelet aggregation in feline whole blood](https://pubmed.ncbi.nlm.nih.gov/41070220/). Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2025. 6. [Applicability of Global Hemostatic Tools for Evaluation of Hemostatic State and Detection of Thrombosis in Cats With Cardiomyopathies](https://pubmed.ncbi.nlm.nih.gov/40976873/). Journal of veterinary internal medicine, 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)