The effect of 25 grams i.v. glucose on serum inorganic phosphate levels

To determine whether a 25-g IV glucose bolus will result in a fall in serum inorganic phosphate levels.

Single-blind, randomized, controlled trial.

Thirty-six healthy, nondiabetic, adult volunteers.

Random allocation to a control group receiving a 50-mL normal saline bolus followed by a normal saline infusion at 125 mL/hr for three hours; study group 1, receiving a 50-mL bolus of D50W followed by a normal saline infusion at 125 mL/hr for three hours; or study group 2, receiving a 50-mL bolus of D50W followed by an infusion of 2/3:1/3 dextrose:saline solution at 125 mL/hr for three hours.

Serum inorganic phosphate levels were measured at time zero (baseline) and at 30-minute intervals for three hours. There was a statistically significant fall in serum inorganic phosphate levels in both groups receiving the glucose bolus. The group receiving the glucose infusion demonstrated a trend toward a further decline in serum phosphate levels.

A glucose bolus and infusion in the amounts compatible with what is given to patients with altered levels of consciousness produced a significant fall in serum inorganic phosphate levels in healthy, nondiabetic adults. Because hypophosphatemia may create a clinical picture of altered mental status very similar to that of hypoglycemia, consideration should be given to administering IV glucose only to patients with finger-stick-proven hypoglycemia. Consideration also should be given to monitoring phosphate levels after administration of IV glucose.