The effect of pH and time on the stability of heparin sodium in dextrose 5% in water (D5W) injection and in dextrose 5% in 0.45% sodium chloride injection was studied. Admixtures of heparin sodium 5,000 units/250 ml were tested after 0, 10, 20 and 30 minutes and 1, 2, 6, 12 and 24 hours of storage at room temperature. The pH of the carrier solutions was adjusted to 2, 4 or 9 prior to adding the heparin sodium. Heparin activity was measured using a thrombin clotting time assay. Samples were tested for pH changes at the same times. No substantial changes in heparin activity over the 24-hour period occurred with any of the pH-adjusted solutions. The pH of the heparin-D5W admixtures remained constant over time. The two carrier solutions, over a pH range of 2 to 9, appear to be suitable vehicles for heparin sodium.