Dog Pooping Blood: Causes, Red vs. Black Stool and When to See the Vet

What the color of the blood means

The color hints at where the bleeding is coming from:

Bright red blood (hematochezia). It usually comes from the end of the digestive tract: the colon, rectum or anus. It can show up as streaks of blood in otherwise normal stool.
Black, tarry stool (melena). This is blood that has been swallowed and digested, so it comes from higher up: the stomach or small intestine.
Blood with no stool, or jelly-like bloody diarrhea. If it's mostly blood, or a jelly-like mass of bloody diarrhea, treat it as serious.

If you see the blood when your dog pees, not in the poop, read dog peeing blood.

Watch out: some foods darken stool, like organ meats (liver) or dark meats (beef, venison). To check, wipe the poop with a paper towel: if the mark is dark red or black, treat it as blood.

When to see the vet

Go to the emergency vet right now if your dog:

Has a lot of blood, jelly-like bloody diarrhea, passes only blood with no stool or strains repeatedly.
Vomits (especially repeated vomiting or vomiting blood), is lethargic or weak, won't eat or drink, or has pale gums.
Is a puppy or an unvaccinated dog. Call the clinic before you go, so they can isolate your dog if it's parvo.
May have eaten rat poison, another toxin or a medication. Bring the packaging.
Has a swollen or very painful belly.

Make an appointment today if your dog is bright and eating, but:

You see a streak of red blood in an otherwise normal stool.
The stool is black or tarry (if your dog is also lethargic or vomiting, go to the emergency vet).
Your dog strains to poop (if it also hasn't gone in days, read dog constipated).

The most common causes

Only a vet can tell which one it is. These are the usual suspects:

Colitis (inflammation of the colon). Stool often has mucus and sometimes blood.
Acute hemorrhagic diarrhea syndrome (formerly HGE). It hits suddenly in an otherwise healthy dog: vomiting and bloody diarrhea, often described as "raspberry jam." It's most common in small and toy breeds, like Yorkshire terriers and Maltese. Without treatment, it can be fatal.
Parvovirus. Young (6 weeks to 6 months), unvaccinated or incompletely vaccinated dogs are most at risk. It starts with lethargy and poor appetite, and vomiting and diarrhea follow within 24-48 hours, usually bloody (about 1 in 4 dogs has no blood).
Parasites, like hookworms.
A food change or eating something they shouldn't have.
Problems around the anus, like anal sac infections.
Stomach or intestinal ulcers, which cause black, tarry stool. Causes include anti-inflammatory drugs, foreign objects, kidney disease, liver disease and Addison's disease.
Foreign objects and blockages.
Rat poison. Bleeding can happen inside the body, and lethargy and loss of appetite can show up even before bleeding does.
Other causes: inflammatory bowel disease, pancreatitis, clotting disorders or cancer.

What to do on the way to the vet

Call the clinic and tell them what you're seeing: color, amount, how long and whether there's vomiting.
Write down when you first saw the blood, what it looked like, how many times your dog has pooped and any change in food or surroundings.
Bring a fresh stool sample in a clean container.
Keep your dog warm and quiet. If they're vomiting, don't force food or water.
Don't give human medications, like Pepto-Bismol or Imodium, unless your vet says so. Anti-diarrheal drugs aren't recommended in parvo, for example.
If you think they ate poison, don't make them vomit unless your vet tells you to.

What the vet will do

They'll examine your dog and, depending on the case, run a fecal test (for parasites and parvo), bloodwork and X-rays or an ultrasound. Sometimes they need an endoscopy with biopsies.

Treatment depends on the cause: the foundation for hemorrhagic gastroenteritis and parvo is IV fluids, and your dog may need to stay in the hospital. Other treatments include dewormers for parasites, surgery for a blockage and weeks of vitamin K1 for rat poison. With supportive care, hemorrhagic diarrhea syndrome usually runs its course in a few days, and more than 90% of parvo dogs treated in the hospital survive.

In the US, an emergency exam averages about $135, a fecal test about $58, a blood count about $104, a chemistry panel about $164, X-rays about $172 and an ultrasound about $483. A hospital stay averages about $1,323 at an emergency clinic and $619 at a regular vet clinic (Synchrony/CareCredit 2025-2026 cost study). Costs vary by region and clinic. More in what a vet visit costs.

Frequently asked questions

Is a streak of red blood serious?

Not always: if it's a little fresh blood in an otherwise normal stool and your dog is bright and eating, it may be something mild. Still, a vet needs to see your dog to rule out other causes. Go to the emergency vet if there's a lot of blood or any sign on the list.

Could dark stool just be from food?

Yes: organ meats (liver) and dark meats can darken stool. Wipe with a paper towel and check the color of the mark. If it's black and tarry, or you're not sure, call your vet.

Is it contagious to other dogs?

It depends on the cause. Parvo is highly contagious: it's shed in the stool and the virus can survive in the environment for a long time. If you have other dogs at home, tell your vet.

Can I fast my dog or feed a bland diet at home?

With blood in the stool, talk to your vet first. The fasting and bland diets some sources suggest are for diarrhea in general, not for bloody diarrhea.

Can it be prevented?

The parvo vaccine protects puppies: it's given at 6-8, 10-12 and 14-16 weeks, with a booster at 1 year and then every 3 years. See the puppy vaccination schedule. A consistent diet, no table scraps and changing foods gradually also help.

Sources

This article is for general information and does not replace diagnosis or treatment by a veterinarian. If you are worried about your pet's health, call your vet clinic.