Our objective was to determine the stability of caffeine base in intravenous admixtures and parenteral nutrition solutions at room temperature for 24 hours. Caffeine 10 mg/mL was used in this study. The admixtures included D5W; D5W with NaCl 0.2% injection; D5W with NaCl 0.2% and 20 mEq/L of potassium chloride injection; D10W injection; and D10W with NaCl 0.2% and 5 mEq/L of KCl injection. The parenteral nutrition solutions included 1.1% amino acids with electrolytes; 2.2% amino acids with electrolytes; and 4.25% amino acids with electrolytes. These parenteral nutrition solutions were prepared in D10W. Ten milliliters of caffeine were added to glass test tubes containing 10 mL of various solutions to yield a final concentration of 5 mg/mL. One milliliter aliquots were removed at 0, 2, 4, 8, and 24 hours and caffeine was measured by a stability-indicating HPLC method. The largest change in the concentrations of caffeine was 4.1 percent during the study period. Thus, caffeine injection is stable in various admixtures and parenteral nutrition solutions at room temperature for 24 hours.