Two hormones from the pancreas tell the liver whether to store glucose or release it, and that tug of war holds blood glucose between about 4 and 7.8 mmol/L. Break one side of the loop and the level drifts out of range. Pick a body and an event, then move the clock forward and watch blood glucose, insulin and glucagon.
Blood glucose stays near its set point by negative feedback: insulin lowers it and glucagon raises it, so when either signal fails the level drifts out of range.