Bloody Diarrhea in Dogs

Bloody diarrhea in dogs is a symptom of many underlying problems, and should always be treated as an emergency to ensure nothing serious is happening within your dog's digestive tract.

Determining Where Your Dog Is Bleeding

The color of the blood in your dog's stool can help you determine where in his body the blood is coming from.

  • Red blood denotes bleeding close to, or from, the rectum. This blood is "fresher" and usually much easier to spot. Red blood tells you the bleeding is further down in the digestive tract, such as from the large intestines.
  • Black blood, however, can be a little harder to spot. Diarrhea will appear tar-like and black, because the blood is not fresh and has been digested. This occurs when the bleeding is in top part of the digestive tract.

The Dangers of Bloody Diarrhea

The fact there is blood in the diarrhea is worrying enough. It means there's blood where it doesn't belong, and your vet needs to find out why. Diarrhea in of itself is important to treat; excessive diarrhea can quickly lead to dehydration which, in turn, brings about many other dangerous problems.


Hookworms are intestinal parasites, more common in humid, warm environments. Hookworms attach themselves to the lining of the intestines and feed on blood. While many dewormers can treat hookworms, more serious cases may need further treatment. Bloody diarrhea as a result of hookworms will most likely be black and tarry.

Canine Parvovirus

Parvo is one of the most devastating killers of unvaccinated dogs and puppies. It attacks the intestinal cells. Symptoms other than diarrhea that occur are fever, lethargy, loss of appetite and vomiting. These can all result in quick electrolyte imbalance, dehydration and shock. The prognosis for parvo is never certain, even with aggressive treatment. If you suspect your dog is suffering from parvo, quickly remove him from any area other dogs or cats may inhabit and seek immediate treatment. Bloody diarrhea as a result of canine parvovirus will be red.

Canine Distemper

Distemper is similar to parvo. This virus attacks the brain, lungs and intestinal tract. Fevers, coughing, sneezing and eye/nose discharge are other symptoms of distemper. Diarrhea appears tar-like due to the blood in it. Seizures and/or twitching can occur when the virus has spread to the spinal cord. The prognosis for distemper is very bleak; very few dogs survive it. Bloody diarrhea as a result of distemper can be either red or black and tarry.

Hemorrhagic Gastroenteritis (HGE)

HGE is when a normally healthy dog has a sudden bought of bloody diarrhea. Toy and miniature breeds are most at risk for HGE. Bloody diarrhea as a result of HGE is usually red.

Ingestion of Dangerous Objects

Another cause of intestinal bleeding could be that your dog ingested something that injured his digestive tract, causing the bleeding. Or, he may have eaten something toxic. Bones, for example, pierce the intestines to result in bleeding. Bloody diarrhea as a result of ingesting garbage or other objects can be either red or black depending on where the problem is.

Other Causes of Bloody Diarrhea

There are many other causes to bloody stools in dogs, and your vet will have to determine the cause and the best course of treatment. Other causes can include:

  • Ulcers
  • Tumors
  • Kidney and/or liver failure
  • Pancreatis
  • Addison's disease
  • Heavy metal toxicity