Exercise is the first thing that will tire your dog out – The Vets point out that there is such a thing as too much exercise.
These illnesses can be any number of things, but weakness and lethargy in dogs can generally be attributed to cancer, trauma, an infection, heart disease, diabetes, and many more.
Aging is probably the most common cause of a greater degree of tiredness – sometimes aging dogs are also accompanied by a plethora of health issues because of their age.
You should ensure that your dog has adequate food, filled with as much nutrition as possible.