It is good that you have noticed your dog’s change in behavior and checked for additional symptoms such as his pale gums. It sounds like your dog might be suffering from anemia – a lowering of red blood cells in the blood, which lowers the amount of oxygen being supplied to his body. The first obvious sign of this is usually the loss of color in the gums.

Anemia can have very serious consequences and could be the result of many serious underlying causes, including cancer. Your vet can diagnose anemia by carrying out a blood count and in some cases a blood transfusion is required to stabilize a dog until the underlying cause can be determined. You must take your dog to your veterinarian for a full examination.