A nurse is teaching a client with diabetes mellitus who asks, "Why is it necessary to maintain my blood glucose levels no lower than about 60 mg/dL?" How should the nurse respond?

Choice A rationale: Glucose is a primary fuel source, but the body can also use fatty acids and amino acids for energy through metabolic pathways like beta-oxidation and gluconeogenesis. The brain, however, has a high metabolic rate and is highly dependent on glucose as its main energy substrate because fatty acids cannot cross the blood-brain barrier efficiently. Choice B rationale: The brain is almost exclusively dependent on glucose for its energy needs, as it lacks the ability to store glucose as glycogen and cannot effectively utilize other energy sources like fatty acids. A sustained blood glucose level below the normal range, typically below 60 mg/dL, impairs cerebral function, leading to symptoms like confusion and lethargy. Choice C rationale: The production of red blood cells, a process called erythropoiesis, occurs primarily in the bone marrow. This process is regulated by the hormone erythropoietin and depends on nutrients like iron, vitamin B12, and folic acid. It is not directly linked to a minimum blood glucose level in the way that brain function is. Choice D rationale: Lactic acid is produced during anaerobic metabolism when oxygen supply is insufficient, not due to low blood glucose. While severe hypoglycemia can lead to metabolic disturbances, lactic acidosis is typically associated with conditions like shock or certain metabolic disorders, not directly with low blood glucose levels.