Final answer:
The most common symptom of hypoglycemia in a diabetic client that the nurse should teach about is nervousness, which is an early sign as the body responds to low blood glucose levels.
Step-by-step explanation:
The nurse should teach the diabetic client that the most common symptom of hypoglycemia is nervousness. Hypoglycemia, or low blood sugar, can lead to symptoms such as nervousness, sweating, tremors, and fainting attacks. However, when blood glucose levels become critically low, more severe symptoms such as unconsciousness or death may occur without proper treatment. Nervousness is often one of the first signs as the body reacts to the decreased availability of glucose, which is essential for energy.