Blood in Dog Stool: Why Is My Dog Pooping Blood?

What it usually means

Vets separate blood in stool into two kinds because they point to different parts of the gut. Hematochezia is bright red blood, sometimes with mucus, and usually comes from the lower bowel: the colon, rectum or anus. Melena is black, sticky, tar-like stool, which is digested blood from higher up, in the stomach or small intestine. The AKC suggests wiping a sample on a white paper towel: a red or black smear suggests blood, while dark food such as liver can make stool look dark without any bleeding.

The most common reasons for bright red blood are fairly ordinary: eating garbage or something unusual, a sudden diet change, stress, colitis, intestinal worms such as whipworms and hookworms, anal gland problems, and straining from constipation or diarrhea. More serious causes include parvovirus, acute hemorrhagic diarrhea, swallowed objects, toxins such as rat poison, clotting disorders, inflammatory bowel disease and tumors. Black stool more often points to ulcers, which can follow anti-inflammatory or steroid medicines, or to liver, kidney or hormone disease.

Patterns your vet will want to know about

Colitis, inflammation of the large intestine, has a recognizable pattern. The Merck Veterinary Manual describes frequent, small, urgent stools with mucus and sometimes blood, often with straining, while the dog otherwise eats and acts normally. Signs can come and go. This is one of the most common reasons for a streak of red blood.

A very different picture is sudden vomiting and large amounts of bloody, raspberry-jam-like diarrhea in a previously healthy dog. Merck notes this hemorrhagic form is seen most in young small and toy breeds such as Yorkshire Terriers, Miniature Schnauzers, Maltese and Miniature Poodles, and that dogs can become dehydrated quickly. Note color, amount, frequency, whether there is mucus, your dog's energy and appetite, and anything it may have eaten; a photo and a fresh sample help your vet.

When to call your vet today

Call your vet the same day if you see blood in your dog's stool more than once, if it is mixed through the stool rather than a single streak, if there is mucus and straining, or if the diarrhea lasts more than a day. Call promptly too if your dog takes any anti-inflammatory or steroid medicine, is a senior, or has other symptoms such as weight loss, reduced appetite or vomiting.

If your dog is a puppy or is not fully vaccinated, call immediately rather than waiting, and tell the clinic before arriving, since parvovirus is contagious and many clinics will take you in through a separate entrance.

When it's an emergency

Go to your vet or the nearest emergency vet immediately if your dog passes large amounts of blood, has black tarry stool, has bloody jelly-like diarrhea, is vomiting as well, is weak, lethargic or collapsing, or has pale, white or gray gums. These suggest significant blood loss, severe infection or shock.

It is also an emergency if your dog may have eaten rat or mouse poison, even if it seems well, since some poisons stop blood clotting and cause internal bleeding days later. Bring the packaging, and call ASPCA Animal Poison Control at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661; a fee may apply.

What you can safely do at home

If your dog is bright, eating and has a single small streak of red blood on a normal stool, keep a close eye on the next few bowel movements, keep fresh water available, and call your vet for advice on whether to bring it in. Save a fresh sample in a sealed bag in case the clinic wants to test it, and take a photo.

Do not give human medicines such as anti-diarrhea drugs, aspirin or other pain relievers; some cause stomach bleeding in dogs and can make things worse. Do not give leftover antibiotics or dewormers either. Ask your vet before changing food or fasting your dog, especially a puppy, a small breed or a dog with diabetes.

If your vet asks for a stool sample, a clean poop bag is an easy way to collect a fresh one.

What the vet will likely check

Expect a physical exam, including a rectal exam and a check of the anal glands, and a stool test for worms, giardia and, in puppies, parvovirus. Blood tests show whether there has been significant blood loss, signs of infection, and how the organs and clotting system are working.

Depending on what they find, your vet may recommend X-rays or ultrasound to look for swallowed objects or masses, and sometimes endoscopy or colonoscopy with biopsies for long-running problems. Treatment depends entirely on the cause: deworming, a diet change, fluids for dehydration, medicine to protect the stomach, or hospital care for severe cases.

Prevention

Many bouts of bloody stool start with dietary indiscretion, so keep trash, compost, bones and table scraps out of reach, and change foods gradually over about a week. Keep your dog on the parasite prevention and stool testing schedule your vet recommends, and make sure puppies finish their vaccine series.

Store medicines, rodent bait and household chemicals where your dog cannot reach them, and never give human pain relievers. If your dog has repeated episodes, ask your vet about investigating colitis, food intolerance or other long-term causes rather than treating each episode on its own.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.