Thanks for the additional information. Just so you know, in most areas, the rehoming of dogs under 6 weeks of age is not legal. I'm not sure of the laws in Canada but I'm sure they must be similar. Pups should not really be separated from their mom's until they are at least 8 weeks of age. While a pup may be weaned, those last few weeks teach a dog bite inhibition ans social skills that they learn from mom and their litter mates.
The most common reason for blood in the stool is parasites such as worms or a protozoan infection such as coccidia or giardia. The most common worms found in dogs are: Roundworms, Hookworms, Tapeworms, and Whipworms and Heartworms. In some cases these worms are passed from the mother to the puppy, in other cases such as tapeworms, they are contracted by other methods such as ingesting an infected flea. Most over the counter medicine will only kill one or two types of worms, so your best bet is to take a fecal sample to your vet to determine the type of worms your dog may have and then decide on treatment. Dogs should be checked for worms periodically even if they appear healthy. This is so if your pet does become ill, you are not fighting a worm infestation along with a more serious problem.
For additional information about worms, see this site
Common dewormers are Panacur, which is a prescription product so you need to obtain it from your Vet and it works on roundworms and whipworms. Wormers labeled as Pyrantel Pamoate are the best over the counter medication for roundworms. These dewormers are relatively inexpensive and can be purchased at most pet stores.
Drontal plus is also a prescription product and is used for the treatment of Tapeworms, though dewormers with praziquantel work well against tapeworms.
If the pup is eating and drinking well, I'd go ahead and deworm him as soon as possible. Plan on deworming again in 2 weeks. He should be seen by your vet if possible, but if you can't afford it and he is eating drinking normally get him started on his vaccinations. It takes at least 2 vaccinations 3 weeks apart to even possibly develop immunity to puppyhood diseases like distemper and parvovirus. Starting at 6-8 weeks is recommended. He should also not be around other potentially unvaccinated dogs or in areas where other dogs go until he is fully vaccinated.
Many feed stores sell vaccinations and they are also available online as well at a reduced rate in the US. However, you may not have that option in Canada. I have heard that some vets will sell vaccinations to breeders, so if your friend is a breeder, his vet might sell him a vaccination and allow you to pay for it and administer it yourself.
Coccidia manifests as mild or severe diarrhea depending on how infected they are. If it is severe, there may be blood and mucous in the stool along with voming and loss of appetitie leading to dehydration You can read about it here:
Information on giardia
Symptoms of giardia are diarrhea with possible terrible smell, mucousy stool and sometimes bouts of vomiting.
If you switched the pups food suddenly that could cause a little blood and diarrhea as well. If that is the case, it should clear up in a few days. I would still try and get the pup dewormed as soon as possible.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.
If you have questions in the future that you wish me to answer, you may click here and bookmark the page or make it a favorite. It is best to put my name "JANE" in the question as well.