As we sleep, the body maintains blood glucose levels by synthesizing glucose through:

Through gluconeogenesis. The lactate pass into the blood and is taken up by the liver and oxidized to pyruvate. Gluconeogenesis changes over the pyruvate to glucose which goes once more into the circulatory system, reestablishing that utilized by the erythrocytes. 
Creatures can change over glucose into any carbon-containing particle they are equipped for integrating, while different atoms are fundamentally less adaptable. In creatures, acetyl-CoA can't be utilized as a substrate for gluconeogenesis. Hence, some different particles must be utilized to produce glucose