The patient is exhibiting signs of hypoglycemia, which may be caused by the bolus of glucose-rich feeding directly into the intestines by an enteral tube that is inserted too deeply. An abdominal radiograph would reveal malposition of the feeding tube. Although the patient is experiencing blood glucose alterations, an HbA1c would be unhelpful. A chest radiograph may be appropriate if the patient began experiencing signs of respiratory distress after the initiation of a tube feeding. Serum electrolytes are less helpful than an abdominal radiograph for this patient whose symptoms are likely caused by a malpositioned enteral tube.