A 15-year-old dog is equivalent to about 78-80 years old in humans. Dogs at this stage are already in old age, their overall health will become worse, and all functions will gradually decline. The resistance will also be much worse than before. Owners should take their dogs to the pet hospital for physical examinations regularly. They should pay attention to a balanced diet and nutrition, and allow the dog to maintain a certain amount of exercise. This can effectively maintain the dog's physical condition. If you want to extend the life of a dog, you mainly need careful care from the owner.

How to judge the age of a dog:
1. Look at the dog’s teeth. Dogs under two months old only have deciduous teeth. Dog babies will have deciduous teeth between 5 and 7 months after birth. Will fall out and give birth to permanent teeth.
2. Look at the dog’s eyes. The eyes of puppies are usually very clear without impurities, while the eyes of dogs in their youth are bright, resolute and very energetic. When dogs enter their old age, they are likely to suffer from cataracts.
3. Look at the dog’s body shape. As dogs age, their muscles also change. You can put your hands on both sides of the spine on the dog's back and touch it gently. As the dog ages, fat usually appears on the dog's lower back or waist. There will also be slight muscle atrophy.
4. Look at the dog’s facial expressions. Dogs aged about 1 year old have active expressions, and dogs aged 2-4 years old love to be close to people, full of energy and enthusiasm. Older dogs over 7 years old may notice obvious mental retardation, dull eyes, and unwillingness to move.