What is the effect of glucagon on blood glucose levels?

Glucagon significantly raises blood glucose levels, primarily by stimulating the liver to convert stored glycogen into glucose through a process known as glycogenolysis. Additionally, glucagon promotes gluconeogenesis, which is the production of glucose from non-carbohydrate sources, such as amino acids. This hormone acts as a counterregulatory mechanism to insulin, which lowers blood glucose levels. When blood glucose levels drop, glucagon is secreted to ensure that the body has enough glucose available for energy, especially crucial during fasting or between meals. This process helps maintain homeostasis in blood glucose levels, illustrating glucagon's essential role in glucose metabolism.

The other options reflect incorrect effects of glucagon; for instance, decreasing blood glucose levels would contradict glucagon's primary function. Lack of significant change would also not capture glucagon's active role in elevating glucose levels, and increasing insulin sensitivity is a function of insulin, not glucagon.