Symptoms to Watch for in Your Dog: Blood in the Stool

If you're the kind of person who freaks out at the sight of any blood in your dog's poop, your dog is better off than if the opposite were true. Blood has no business being in the poop.

It is not always the end of the world type of emergency, but it always needs to be taken seriously.

Symptoms to Watch for in Your Dog: Blood in the Stool

How quickly you need to see a vet depends on how much blood there is, and whether there is also diarrhea, vomiting lethargy or other concerning signs.

One drop of blood does not an emergency make, but things can change quickly.

If the blood in your dog's stool looks like actual blood, it is coming from the large intestine, rectum, or nearby structures. If it came from higher up in the gastrointestinal tract, it would not have the typical bright red appearance. Such partially-digested blood would make the stool look dark and tarry.

Dietary indiscretions

A dietary indiscretion, particularly with diarrhea, can irritate the colon enough to cause mucus and even blood in the stool. Even an abrupt change of food can do that to some dogs. JD did this to himself on occasion; his poop would be runny with the odd drop of blood. He'd act normally otherwise, and the problem would resolve itself by the next day. He did not need veterinary treatment.

Jasmine would have a small amount of blood in her diarrhea when her IBD was acting up. She did need medical attention. Just goes to show that the same signs in different dogs can mean very different things.

GI injuries

A foreign body, such as a piece of a stick, a chunk of undigested bone, rocks, and other objects can injure the lining of the gastrointestinal tract and make it bleed. Again, the injury can be minor or major; are you willing to take a wild guess?

One question I always keep in my mind, how much blood there might be that I don't see? Is my dog in pain? Lethargic? Bleeding anywhere else? Having unexplained bruising? Looking swollen?

Hemorrhagic gastroenteritis (HGE)

They recently changed the name of this condition to acute Hemorrhagic Diarrhea Syndrome (AHDS) because it seems that the stomach actually isn't involved with the problem.

Whatever they choose to call it, it doesn't make it any less terrible. Either way, it comes with lots and lots of blood. It's what I meant when I said that a couple of drops of blood don't an emergency make, but this can change in a blink of an eye.

With HGE/AHDS the poop can look like straight blood. Clearly, that is an extreme emergency. That's also while I said that it is better to be paranoid and see a vet with one drop than wait until things might get this bad.

Bloody diarrhea characteristic of acute hemorrhagic diarrhea syndrome. Photo CriticalCareDVM


If a puppy has any amount of blood in the poop, it's an emergency. In fact, a sick puppy is always an emergency no matter the signs. Bloody diarrhea is a common symptom of the dreaded disease parvovirus but can also be seen with a variety of other viral and bacterial diseases that can affect puppies and adult dogs.


The parasites most likely to cause blood in the stool are hookworms, whipworms, Coccidia and Giardia. Sometimes symptoms like diarrhea and a pot-bellied appearance appear first but blood in the stool may be the first indication that a dog has intestinal parasites. Either way, intestinal parasites can kill a dog, particularly a puppy, so never think “oh, it’s probably just worms.”

Another thing that can cause bloody diarrhea is stress.

Stress can not only aggravate any existing problem, such as IBD but even cause what is called stress colitis with bloody diarrhea with mucus.

There are other causes

Inflammation of an anal sac, blood clotting problems, twists or other problems within the gastrointestinal tract, perianal fistulae, polyps, and even cancer can all cause blood in/on the stool.

If you're an experienced dog parent, you might be able to tell when a few drops of blood are not a big deal and when you should see a vet as soon as possible. Even then I always tend to err on the side of caution. I'd recommend to at least talk to your veterinarian if you find blood in your dog's poop.

Do you know what your dog is telling you about their health?

Learn how to detect and interpret the signs of a potential problem.

Symptoms to Watch for in Your Dog now available in paperback and Kindle. Each chapter includes notes on when it is an emergency.

Symptoms to Watch for in Your Dog is an award-winning guide to help you better understand what your dog is telling you about their health and how to best advocate for them. 

Learn how to see and how to think about changes in your dog’s appearance, habits, and behavior. Some signs that might not trigger your concern can be important indicators that your dog needs to see a veterinarian right away. Other symptoms, while hard to miss, such as diarrhea, vomiting, or limping, are easy to spot but can have a laundry list of potential causes, some of them serious or even life-threatening. 

Symptoms to Watch for in Your Dog is a dog health advocacy guide 101. It covers a variety of common symptoms, including when each of them might be an emergency. 

Symptoms to Watch for in Your Dog has won the following awards:


  1. Thanks for such an important post, and something I'm quite familiar with. A couple of weeks ago I noticed blood in Red's poop. She had already been slightly off her food, and I knew that meant another mild flare up of her chronic pancreatitis, but this was something different. It meant she was bleeding from somewhere, and my vet determined it was an ulcer. I always learn a lot from your "symptoms" posts.

    1. So sorry about Red. Glad you were on top of it though. I hope she feels better soon.

  2. Very informative post. I am curious, would most of these causes apply to blood in a cat's poop as well?

    1. Technically, yes. Bleeding is generally either damage to tissues that makes blood leak, or issues with clotting that makes blood leak. While the specific conditions in cats might be different, some might be the same but the mechanics are the same I'm sure.

  3. Knowing there are less frightening options than 'fatal' is what every dog owner wants to hear. A pet parent might go off the deep end and worry themselves into a frazzle if they did not know that there are other options that make a lot of sense.

    1. Yes, fortunately, not everything that looks scary is fatal. Though it could be. So it's good to stay on top of things.

  4. Great post as always and I do worry if I see blood and am the first at the vet about it or emailing him about it

  5. Bernie has had blood in his poop after his Addison's flares up. And yes, it's scary looking. I had to remind myself that he had vomited with some blood flecks, we had treated him, and the remaining blood from the episode was making its way out of his system with his poop.

    1. Sorry about Bernie having a hard time. One thing, though, blood from the stomach would not come out looking like blood in the stool; gets digested along the way and no longer looks red and bright but black; hence tarry stools. Blood that looks like blood does come form the intestine or rectum.

  6. Great information. I didn't know there were so many diseases that can lead to bloody poop, even Giardia!.I've never had too much of a problem, just a bit of fresh blood that usually went away quickly. I figured my senior dog either had hemorrhoids or dragged his butt in something. Usually it was just a few drops.

    1. Due to the difference in their anatomy, dogs are actually quite unlikely to get hemorrhoids. It is very likely it was something else. I wrote an article about that recently.

  7. the input and output of our animals is so important to keep an eye on.


Post a Comment