The order is to infuse 1000 units heparin per hour from an available solution strength of 25,000 units in 500 ml D5W. Calculate the ml/hr rate. 500ml\25000 x 1000\1 =20 ml\hr. 2. A solution of 25,000 units heparin in 500 ml D5W to infuse at a rate of 1200 units per hour. Calculate the ml/hr rate.