Site Accessibility Features: Skip to page menus
Site Menus Section Skip to page content
Most bleeding (hemorrhage) is caused by trauma. A wound or a history of injury usually explains why a pet is bleeding. Typically, the bleeding stops when a blood clot forms at the injury site. However, sometimes bleeding occurs when there is no wound and no history of injury. In these cases, the bleeding cannot be explained.
For example, a pet may suddenly start bleeding from the nose or pass blood in the urine for no apparent reason. There is often bleeding under the skin or on the gums, seen as tiny, pinpoint spots of hemorrhage called petechiae or larger blotches called ecchymoses.
Unexplained bleeding is worrisome because it suggests a problem with the body’s blood clotting or coagulation system. Disorders of the coagulation system can arise for many reasons, including shortages of coagulation factors (clotting proteins), a shortage of platelets (a type of blood cell), defective platelets, and serious systemic disease affecting the whole body.
The search for answers starts with a complete history and physical examination. A pet’s history is the information you give the veterinarian about your pet’s illness. For example, it would be important to mention whether your pet has had contact with rat poison or is known to hunt for mice or rats. You would also want to mention medications or supplements your pet has received recently or describe any signs of illness your pet is showing.
> "The search for answers starts with a complete history and physical examination."A physical examination involves looking at all parts of the body, checking for petechiae and ecchymoses, listening to the heart and lungs with a stethoscope, and palpating the abdomen (gently squeezing or prodding the abdomen with the fingertips to detect abnormalities of the internal organs). In dogs, it is essential to note if they are purebred, as they are more likely to have hereditary blood clotting problems.
If the cause of the bleeding cannot be found, your veterinarian may recommend screening tests. These simple tests provide information about the pet’s overall health and may provide further clues about the underlying problem.
The most common screening tests include complete blood count (CBC), serum biochemistry profile, and urinalysis. In addition, special tests to evaluate the coagulation system may be recommended, including coagulation profile, Von Willebrand's factor assay (in dogs), and possibly buccal mucosal bleeding time (BMBT).
The CBC provides information about the three cell types in the blood: red blood cells, which carry oxygen to the tissues; white blood cells, which fight infection and respond to inflammation; and platelets, which help the blood clot. The CBC provides details about the number, size, and shape of the various cell types and identifies the presence of abnormal cells. See the handout “Complete Blood Count” for more information.
In a pet with unexplained bleeding, the most essential information is the platelet count, a measure of the number of platelets in the blood. Platelets are an essential part of the coagulation process, and if the platelet count is too low, then unexplained bleeding may develop. A low platelet count is called thrombocytopenia. There are many causes of thrombocytopenia. A few examples include immune-mediated destruction of platelets, decreased production of platelets in the bone marrow, and increased use of platelets by the body.
> "In a pet with unexplained bleeding, the most essential information is the platelet count, > > a measure of the number of platelets in the blood."Sometimes, the CBC provides clues about the cause of thrombocytopenia. For example, if too many white blood cells are in the blood, severe inflammation or infection may be present, which can cause thrombocytopenia. If there are too few white blood cells, a viral infection may be damaging the bone marrow, causing platelet numbers to fall. If there are abnormal cells in the blood, leukemia (bone marrow cancer) may be causing thrombocytopenia.
The CBC also counts the number of red blood cells in the blood. If bleeding is severe or has been going on for a long time, the number of red blood cells may be deficient. Specific treatment, such as a blood transfusion, may be needed to bring the number of red blood cells back to normal.
Serum biochemistry refers to the chemical analysis of serum (the pale-yellow liquid part of blood that remains after the cells and clotting factors have been removed). The serum contains many substances, including enzymes, proteins, lipids (fats), glucose (sugar), hormones, electrolytes, and metabolic waste products. Testing for these substances provides information about the health of various organs and tissues in the body, as well as the metabolic state of the animal.
Changes and abnormalities found in the biochemistry profile can help diagnose various diseases and disorders. See the handout “Serum Biochemistry” for more information.
Urinalysis is a simple test that analyzes urine's physical and chemical composition. It measures how well the kidneys are working, identifies inflammation and infection in the urinary system, and helps detect diabetes and other metabolic disturbances. Urinalysis is necessary for adequately interpreting the serum biochemistry profile and should be done at the same time as blood testing. See the handout “Urinalysis” for more information.
Severe systemic diseases like liver or kidney failure can interfere with normal coagulation. Serum biochemistry and urinalysis help to determine if such diseases are present and might be causing a pet’s unexplained bleeding.
Sometimes a patient will have a normal amount of platelets, but the BMBT is abnormal. This indicates a platelet function defect, which means the platelets are not working correctly and can’t form a platelet plug. Some drugs, such as aspirin, interfere with platelet function and can lead to unexplained bleeding.
Screening and coagulation tests will likely identify the cause of the unexplained bleeding. However, there may be underlying problems that need to be investigated further. Some examples:
© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Last updated on Oct 3, 2022.
Site Sidebar: Skip to end of sidebar
Search Articles
Filter By Species
View All
© 2025 Glen Park Animal Hospital. Provided by Patterson | Powered by LifeLearn WebDVM