I'm not a vet...but take your puppy to the vet ASAP....as this could be a very dangerous illness called Parvovirus. A few weeks after we gor our puppy, she became very ill with this virus and almost died. If it's parvo, your vet can help, but you need to get him there fast, in order to start treatment as quickly as possible....Parvovirus infection is often fatal..and the risk of dehydration as a secondary potential problem, is far too great to wait. As I said...I'm not a vet...but I am a Registered Nurse, and worked at a vet hospital to pay my way through school. Good Luck!
Blood in stool is not normal and is a cause for concern in any dog especially a young puppy like yours.
Please see your vet ASAP.
This may or may not be an adverse vaccine reaction which your vet can address and correct.
Dr Carol Osborne, DVM
I am not the Vet, but you may not have time to wait for their response.....
Yes, you need to worry!!! Pooping blood is NOT NORMAL in any species....Get your guy back to your Vet ASAP....Dehydration in young puppies can be a serious complication if left untreated.....
Come back and let us know what you find out...Good luck.....