What causes a dog to sleep excessively?

Excessive sleep in dogs may be due to being very young or very old, when low energy means they can sleep 10-20 hours a day. Second, sick dogs also tend to sleep a lot; if you notice fever, runny nose, sneezing, vomiting, diarrhea, or decreased appetite, take the dog to a vet promptly.

Finally, dogs may sleep excessively when their living environment changes, because they have not adapted and choose to curl up in a corner; this usually returns to normal after about 2 days of adjustment.