5. Lethargy

It is a known fact that older dogs slow down. As they age, their bodies change, and, with it, all of their processes slow down. It is completely normal for your old dog to not be as active as he used to be a few years ago.

But if you see that your friend is suddenly more tired and seems to not enjoy the things that made him happy just a few days ago, you should be careful because fatigue can signal illness.

Lethargy is different from the usual fatigue. A lethargic dog will lose all of his enthusiasm. He might start to sleep most of the time, refuse to eat, and even refuse to walk around or play with his favorite toy.

Even if your dog is lethargic, this doesn’t mean that he is suffering from cancer. There are many other diseases out there that can cause lethargy, and cancer is only one of them. But you can never be sure without taking your friend to the vet.