Originally Posted by selzer
I hope this is not the case for you. The runt of the litter is usually fiesty, and a survivor, and they often catch up before a litter goes home, but a true-runt often has health problems.
on the opposite end of that....Riley was the largest of the litter and had a lot of health problems. I don't know how the rest of the litter fared. He was about 7 pounds at 8 weeks. All the puppies there were very skinny. I think it depends on the genes they get and how do you know that in advance?
I hope the op's puppy is healthy and just small, but I would take it to a vet.