Complex sentence: This is caused by low glucose levels in the blood, after exhaustion of cellular carbohydrate stores, such as glycogen, synthesis of ketones can occur due to excessively high levels of blood glucose that are unable to be stored as glycogen in liver and muscle.
Split into simpler sentences: This is caused by low glucose levels in the blood, after exhaustion of cellular carbohydrate stores, such as glycogen. Synthesis of ketones can also occur due to excessively high levels of blood glucose that are unable to be stored as glycogen in liver and muscle.