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What Are the Causes of Blood in Dog Stool?

| Updated September 26, 2017

A dog can suffer health problems over their lifetime. Finding blood in your dog's stool for can be cause for alarm. The condition is usually caused by a number of factors such as intestinal parasites, viral infections, bacterial infections, fungal infections, colitis, anal sac disease, cancer, hemorrhagic gastroenteritis, bleeding disorders, and adverse drug reactions. Blood in a stool can also indicate different problems based on the dogs age; for example blood in an older dogs stool could mean cancer while in a younger dog it could indicate a parasite problem.


Detecting blood in your dogs stool may vary from a few red drops to a few streaks of blood on your dog's feces. The blood can come in bright red, dark red to black colored stools. Red blood indicates hematochezia while black stools indicate melena, which is bleeding in the upper part of the intestines.


Finding a blood does not always mean your dog is sick. For example, after chewing on bones or sticks, sharp fragments can injure the intestinal lining, causing it to bleed. The bleeding subsides after the dog has passes it through their digestion track. Dogs sometimes pass black, tarry stools because they ingested blood. They might have a bloody mouth injury or licked blood off a body wound.


Parasites are the most common cause of blood in a puppy's stool. Some common canine parasites include roundworms, whipworms and hookworms. More common diagnosis for older dogs, canine cancers such as colon cancers can cause dogs to pass dark black stools.


Parvo is a virus that is a serious canine health condition causing blood in the stools as well as lethargy, appetite loss, diarrhea and vomiting. Blood clotting disorders, or coagulopathies, might cause a dog to bleed internally and pass bloody stools. This can be caused by hemophilia, liver disorders or organ failure.


Once you notice blood in your dog's stool, take notice of the blood color (bright red, dark red or black) and whether it's on the surface or mixed within the feces. Is the amount of blood a small amount or a puddle? Save the fecal sample for your veterinarian to investigate within 24 hours.