My puppy seems to be overly tired and sleepy....
Hi
Lethargy is one of the most common symptoms that puppies show when they're sick. There are a whole host of dog illnesses that young puppies are vulnerable to before they have had all their puppy shots.
If your pup isn't fully vaccinated and this is unusual behavior for him, and/or if he's showing any other signs of illness, please get him to a veterinarian immediately so that you can find out what's wrong.
There is another situation with new puppies where lethargy can appear and not necessarily be related to illness. It may be seen during the first few days after a puppy comes into his new home and is a reaction to the stress that the changes in his situation and surroundings. You can learn more about this on my Bringing Home A New Puppy page.
However, it's always better to be safe than sorry as young puppies can get very sick, very fast. If you are at all worried about your little guy, get your vets' help asap.
Best of luck with your pup.