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My dog threw up, has dark runny stool. Is it serious or just sensitive stomach?

Updated On September 23rd, 2025

Pet's info: Dog | German Shepherd | Male | 70 lbs

My dog (German Shepherd) threw up Friday night and had a very loose stool. He did not eat all Saturday and was very subdued. Today he is much more perky and ate a little food. However his stool is very runny, dark black or even a reddish brown. (See picture.). He has continued to drink plenty of water the whole time. In general he has had a sensitive stomach. But he hasn’t thrown up or had this kind of store before.

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2 Answers

Most Helpful Answer

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Answered By Dr. Davis

Veterinarian

Published on October 15th, 2017

I'm concerned about this stool. Dark tarry stool like this can be a sign of stomach or intestinal bleeding. The bleeding could be from medication, parasites, a gastric ulcer or cancer. I'm glad Truman is feeling better but I recommend a veterinary exam soon. They will run a blood panel to check for anemia, perhaps check for intestinal parasites, and perhaps due some X-rays. It's important to find the cause of this so this doesn't become a more serious medical problem. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Truman.

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    Answered By Daniel Fonza, DVM

    Veterinarian

    Published on

    Hi there and thank you for using pet coach to address your concern. Judging from your description and history as well as the photo, it sounds to me as though he has a bit of gastroenteritis. The blood in the stool is likely secondary to the diarrhea. I am unsure as to what caused the vomiting and runny stool but I would recommend starting a bland diet of chicken, rice and egg. I would also add a probiotic such as Purina fortiflora. Feed the Bland diets and probiotic at least 3 days beyond the resolution of the diarrhea. If the blood in the stool becomes more voluminous and he worsens, I would get him examined by a veterinarian to have further testing done. If you just switched dog foods or introduced a new treat or type of food then this could be what led to the vomiting and diarrhea. If that is the case, I would transition back to the original Diet before the switch or eliminate any nutrients that you have added in to prevent this from happening again as this could be dietary indiscretion secondary to a new food. I hope this helps! Please feel free to contact me with any other questions or concerns that you may have.

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