Nurse starts heparin infusion 3000 units/hour; pharmacy sent 25,000 units/500 mL; at what rate in mL/hour?

• A. 50 mL/hour
• B. 60 mL/hour
• C. 75 mL/hour
• D. 40 mL/hour

Answer: (B)

Converting a rate from units per hour to milliliters per hour uses the solution’s concentration. The infusion has 25,000 units in 500 mL, which is 25,000 ÷ 500 = 50 units per milliliter. To deliver 3,000 units each hour, divide 3,000 by 50, giving 60 mL per hour. So set the infusion to 60 mL/hour. Quick check: 60 mL/hour × 50 U/mL = 3,000 U/hour, matching the prescribed rate.