Why Does My Dog Have Blood in His Stool?

Blood in your dog's stool is never considered normal and should always be taken seriously. While a small amount of bright red blood may be caused by irritation of the lower bowel, blood in the stool can also indicate infections, intestinal parasites, dietary indiscretion, haemorrhagic gastroenteritis, poisoning, or more serious gastrointestinal disease. If your dog has repeated bloody diarrhoea, large amounts of blood, black tarry stools, or appears unwell, seek veterinary attention immediately.

Blood in the stool can range from mild irritation to a medical emergency.

A small streak of bright red blood may result from straining or inflammation of the large intestine. However, large amounts of blood or black, tarry stools often indicate more serious disease and require prompt veterinary assessment.

The colour of the blood helps determine where the bleeding is coming from.

Bright red blood usually originates from the lower digestive tract, while black or tarry stools often indicate bleeding higher up in the stomach or small intestine. Both should be investigated by a veterinarian.

Bloody stools accompanied by vomiting or lethargy require urgent veterinary care.

If your dog has blood in their stool together with vomiting, weakness, loss of appetite, pale gums, or collapse, they may have a serious illness requiring immediate treatment.

Why does my dog have blood in their poop?

Blood in a dog's stool is a symptom rather than a diagnosis. It occurs when there is bleeding somewhere within the digestive tract. The cause may be mild and self-limiting, or it may indicate a serious medical condition requiring urgent treatment.

Common causes include:

• Colitis (large bowel inflammation)

• Dietary indiscretion

• Sudden diet changes

• Intestinal parasites

• Bacterial infections

• Viral infections (such as parvovirus)

• Haemorrhagic gastroenteritis (AHDS)

• Foreign body ingestion

• Food allergies

• Stress colitis

• Anal gland disease

• Intestinal tumours

• Bleeding disorders

• Rat bait or other toxin ingestion

What does the colour of the blood in my dog's stool mean?

The appearance of the blood provides important clues about where the bleeding may be occurring, but it cannot identify the underlying cause on its own. Your veterinarian will also consider your dog's history, physical examination, and diagnostic test results.

Any blood in your dog's stool warrants attention, but certain situations are more urgent than others. Large amounts of blood, black tarry stools, repeated bloody diarrhoea, or blood accompanied by vomiting, weakness, or collapse should be treated as emergencies.

Why does my dog have bright red blood in their poop?

Bright red blood, known as hematochezia, usually comes from the lower part of the digestive tract.

Common causes include:

• Colitis

• Rectal irritation

• Constipation and straining

• Anal gland disease

• Intestinal parasites

• Dietary indiscretion

Although some causes are relatively mild, persistent bleeding should always be investigated.

Why is my dog's poop black and tarry?

Black, tarry stool known as melena, often indicates bleeding from the stomach or small intestine.

Possible causes include:

• Stomach ulcers

• Severe gastrointestinal disease

• Certain medications

• Bleeding disorders

• Tumours

• Foreign body injuries

Melena is considered a medical emergency because it may indicate significant internal bleeding.

Why does my dog have bloody diarrhoea?

Bloody diarrhoea is commonly associated with inflammation or infection of the intestines.

Possible causes include:

• Acute haemorrhagic diarrhoea syndrome (AHDS)

• Parvovirus

• Intestinal parasites

• Bacterial infections

• Severe colitis

• Toxin ingestion

Dogs with bloody diarrhoea can become dehydrated rapidly and should be examined promptly.

Could my dog have eaten something they shouldn't?

Yes. Dietary indiscretion is a common cause of bloody stools.

Examples include:

• Garbage

• Spoiled food

• Bones

• Sharp objects

• Toxic plants

• Rat bait

• Household chemicals

Foreign bodies and toxins can damage the intestinal lining and cause bleeding.

How will a veterinarian determine the cause?

Your veterinarian will begin with a detailed history and physical examination.

Depending on your dog's symptoms, they may recommend:

• Faecal examination

• Blood tests

• Clotting tests

• Parvovirus testing

• X-rays

• Ultrasound

• Endoscopy (selected cases)

• Biopsy (selected cases)

These tests help determine the source of bleeding and guide the most appropriate treatment.

How is blood in a dog's stool treated?

Treatment depends on the underlying cause of the bleeding rather than the blood itself. Some dogs recover with supportive care, while others require hospitalisation, surgery, or intensive medical treatment. Your veterinarian will first identify the cause before recommending treatment.

The table below outlines some common causes of bloody stools and the treatments that may be recommended.

Blood in the stool is a symptom, not a diagnosis. Simply stopping the bleeding without identifying the underlying cause may delay appropriate treatment and allow serious conditions such as intestinal obstruction, severe infection, poisoning, or gastrointestinal disease to worsen. Early diagnosis improves the likelihood of a successful outcome.

Can I monitor my dog at home?

Some dogs with a single small streak of bright red blood and no other symptoms may be monitored briefly.

Home monitoring may be appropriate if your dog:

• Has only a small amount of bright red blood

• Remains bright and alert

• Continues eating and drinking normally

• Has no vomiting

• Has normal energy levels

If bleeding continues, worsens, or additional symptoms develop, arrange a veterinary examination promptly.

If my dog has blood in his stool, should I monitor or visit the veterinarian?

Blood in your dog's stool should never be ignored. While some cases are mild, others require urgent treatment. Use the guide below as a general reference. If you are unsure, it is always safest to contact your veterinarian.

Contact a veterinarian immediately if your dog has repeated bloody diarrhoea, black tarry stools, large amounts of blood, vomiting, weakness, pale gums, collapse, or if they are a puppy or senior dog. Even mild bleeding that persists should be investigated. Early diagnosis can identify the cause, prevent complications, and improve your dog's chances of a full recovery.

Frequently Asked Questions

Can stress cause blood in my dog's stool?

Yes. Stress can sometimes trigger inflammation of the large intestine, known as stress colitis, which may result in diarrhoea containing small amounts of bright red blood. However, other medical causes should always be ruled out before assuming stress is responsible.

Can worms cause blood in my dog's poop?

Yes. Intestinal parasites such as hookworms, whipworms, and other parasites can irritate or damage the intestinal lining, leading to bloody stools. A faecal examination can help identify the parasite responsible.

Can food allergies cause bloody stools?

Yes. Some dogs with food allergies or food intolerances develop inflammation of the intestines, resulting in diarrhoea that may occasionally contain blood. Your veterinarian may recommend a dietary trial if a food allergy is suspected.