This is a question that you and your veterinarian should discuss. Your veterinarian will leave the final decision up to you. There are cases where immediate euthanasia may clearly be indicated, for example, if the animal is clearly struggling and in obvious pain, or has been severely injured and medical intervention will not help. In other cases, as in a prolonged illness like cancer, you may be able to have more time with your pet, provided you can maintain some quality of life and keep any pain under control. Quality of life and pain control are the standards on which you should base any decisions concerning euthanasia.