How To Tell If Your Dog Is Sick Or Just Tired. It's usually fairly easy to tell if your dog is acting sluggish. Prolonged lethargy is a strong sign that your pooch isn’t feeling well.

There is often a cross over in symptoms between depression and sickness, and it is not always easy to tell the difference because both sick and depressed dogs tend to be off their food, and are reluctant to exercise. Signs of a fever can include a warm and dry nose, red eyes, lack of energy, warm ears, and shivering. If your dog is behaving in an unusual manner, it is wise to get them checked out by a vet.