[header] How to determine if you should euthanize your dog [title] Assess your dog's bodily condition. [step] You may want to consider euthanizing a dog that is withering away and is losing its ability to move. Loss of mobility and excessive weight loss are signs that your dog's body is shutting down. 
As your dog loses weight and loses the ability to move, its quality of life also suffers. [substeps] Discuss the reasons for weight loss with your veterinarian.