It’s not just about “dog years.” When your dog is considered a senior depends on factors such as their breed, size, and overall health. Large-breed dogs are often considered senior before their small-breed cousins, which makes sense because large-breed dogs typically have shorter overall lifespans. In general, however, a dog or cat can be considered middle aged around 7 years of age, and officially become a senior around 11 (although, again, this does depend somewhat on their breed). If you suspect your dog is beginning to show signs of slowing down, showing symptoms of a condition such as arthritis, or experiencing behavior changes, make an appointment with your vet to talk about what you can do to help them transition.