Aging does vary by breed, and small breeds generally live longer than large breeds. A small dog isn’t considered elderly until eight to nine years; a large dog is usually considered a senior at five to seven years old. Your veterinarian can help you make a more accurate estimate of your pet’s age if they are a rescue.

You can expect a senior dog to gradually become slower and weaker. Their sense of sight, smell, taste, and hearing may also decrease in strength. They will also take longer to recover from an illness or an injury, which is why it is important to watch for problems and begin treatment as soon as you detect any trouble.