It is time to put a dog to sleep when his discomfort surpasses its ability to enjoy life, states the ASPCA. A veterinarian is the best-qualified person to help make this decision, as medical tests often provide more information about a dog's medical status than owner observation.
Uncontrollable chronic pain, frequent vomiting and/or diarrhea, weight loss and refusal to eat are some signs that indicate a dog is suffering or experiencing a poor quality of life, explains the American Humane Association. Other signs include incontinence, chronic coughing or breathing difficulties, lack of interest in activities previously enjoyed, and the inability to stand or walk on its own. The ASPCA notes that minimizing the dog's suffering is the goal, and keeping a daily record of its activities and behavior can help the dog owner and veterinarian decide when it is time to help the dog pass.