Calculate the rate in drips per minute (gtt/min) for an infusion of 150 mL/hr with a drop factor of 15 gtt/mL.

Calculate the rate in drips per minute (gtt/min) for an infusion of 150 mL/hr with a drop factor of 15 gtt/mL.

• A. 25 gtt/min
• B. 38 gtt/min
• C. 50 gtt/min
• D. 60 gtt/min

Answer: (B)

Understanding how to convert a mL per hour infusion into drops per minute is the key. The rate in gtt/min is found by multiplying the infusion rate (mL/hour) by the drop factor (gtt/mL) and then dividing by 60 to convert hours to minutes. Compute: 150 mL/hour × 15 gtt/mL = 2250 gtt/hour. Then 2250 gtt/hour ÷ 60 minutes/hour = 37.5 gtt/min. Since you can’t deliver half a drop, round to the nearest whole drop: 38 gtt/min. A quick check helps: 150 mL/hour equals 2.5 mL/min; with 15 drops per mL, that’s 2.5 × 15 = 37.5 gtt/min, which rounds to 38.

Understanding how to convert a mL per hour infusion into drops per minute is the key. The rate in gtt/min is found by multiplying the infusion rate (mL/hour) by the drop factor (gtt/mL) and then dividing by 60 to convert hours to minutes.

Compute: 150 mL/hour × 15 gtt/mL = 2250 gtt/hour. Then 2250 gtt/hour ÷ 60 minutes/hour = 37.5 gtt/min. Since you can’t deliver half a drop, round to the nearest whole drop: 38 gtt/min.

A quick check helps: 150 mL/hour equals 2.5 mL/min; with 15 drops per mL, that’s 2.5 × 15 = 37.5 gtt/min, which rounds to 38.