As part of homeostasis, it is vital for the human body to maintain blood glucose levels within a narrow range. The 2 main hormones involved are insulin, when glucose levels are too high, and glucagon, when glucose levels are too low. They're both released by the pancreas. When glucose concentrations are too high, insulin is released, which causes glucose uptake by cells and the conversion of glucose to glycogen, to be stored. This lowers blood glucose levels. When glucose concentrations are too low, glucagon is released, which converts glycogen to glucose, and releases glucose into the bloodstream, to increase blood glucose levels.