Why Is a Dog Vomiting Blood?

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The presence of blood in vomit is called hematemesis. A variety of things can cause a dog to vomit blood. Not all causes are life threatening, but if you find that your dog is vomiting up pure blood or there is the presence of blood in the vomit, seek professional help if the condition continues.

Blood in a dog's vomit can be bright red or a brown colour.

Stomach ulcers

Ulcers in the stomach lining can cause a dog to vomit blood. Dogs taking non-steroidal anti-inflammatory drugs (NSAIDs) for disorders, such as arthritis or tendinitis, are particularly at risk. NSAIDs inhibit the production of prostaglandins, which play an important role in protecting the lining of the stomach. Without prostaglandin production, stomach acid can gradually wear away at the stomach lining, causing ulcers. Stress can cause stomach ulcers as well. Helicobacter is a bacteria in the stomach that can casue inflammation and ulcers. "One of the best ways to treat ulcers in dogs is through natural remedies such as aloe vera and liquorice root," said Bastian Harnik, a veterinarian at Village Veterinary Practice in London. "Aloe vera treats nausea, helps the ulcers heal and can be added easily to the dog's water at a rate of two teaspoons a day. Liquorice root helps stimulate cell growth, protects the stomach walls and calms the pain of ulcers." Harnik also recommends giving L-glutamine to dogs taking NSAIDs. This amino acid strengthens and protects the stomach wall.


Toxins such as rat poison can cause a dog to vomit blood. Nosebleeds and rectal bleeding accompanied by dark stool are a tell-tale sign that your dog has been exposed to poison. Many household items lying around a home can prove to be toxic to dogs---insect killer, antifreeze and sugar-free candies. If you suspect that your dog ingested something toxic, call a veterinarian immediately. The veterinarian may suggest inducing vomiting by giving the dog one tsp of three-per cent hydrogen peroxide for every 4.54 Kilogram of the dog's body weight, Harnik said. The dog may be put on IV fluids to help its body rid itself of the toxin, Harnik said.


Obstructions caused by foreign bodies, such a child's toy, can damage the lining of the stomach and oesophagus. "The intestine can also be damaged as the object passes through the digestive system," Harnik said. "If this is the case, the blood will be fresh looking and it is essential you get the dog to the vet as soon as possible."


Cancerous tumours can cause bleeding in the stomach, oesophagus or duodenum (the first part of the small intestine). Benign tumours can cause obstructions to the digestive system that can lead to bruising of the stomach lining or oesophagus, causing blood to be present in vomit.

Clotting disorder

If your dog is vomiting up blood daily, it might have a blood clotting disorder. Look for other signs of bleeding, a purplish tint to his skin and broken capillaries, which like red spider webs just under the surface of the skin.


Sometimes retching is enough to cause bleeding. You will find small flecks of fresh blood in the vomit, but it should only be temporary.

Other causes

Blood may be coming from the mouth or throat, caused by chewing on something sharp. Blood can also be passed into vomit by blood swallowed from a nose bleed. Inspect your dog's nose and mouth areas to identify the source of blood.