In both humans and dogs, the level of blood sugar is controlled by the release of insulin from the pancreas. Xylitol does not stimulate the release of insulin from the pancreas in humans, but it does in dogs. The sudden release of insulin causes a rapid and profound decrease in the level of blood sugar (hypoglycemia), within 10-60 minutes of eating the xylitol. Untreated, this hypoglycemia can be life-threatening. The most common source of xylitol poisoning that Pet Poison Helpline gets calls about comes from sugar-free gum.