If a patient required 150 mL infused over 1 hour and the drop factor were 10 gtt/mL, the drip rate would be approximately how many drops per minute?

• A. 15 gtt/min
• B. 25 gtt/min
• C. 38 gtt/min
• D. 60 gtt/min

Answer: (B)

Drip rate in drops per minute is found by multiplying the volume to be infused by the drop factor, then dividing by the infusion time. Here, 150 mL over 60 minutes with a drop factor of 10 gtt/mL gives: (150 × 10) / 60 = 1500 / 60 = 25 gtt/min. Another way to see it is 150 mL/60 min = 2.5 mL/min, and 2.5 mL/min × 10 gtt/mL = 25 gtt/min. So the infusion should run at 25 drops per minute. Rates like 15, 38, or 60 gtt/min would not deliver the same 150 mL in one hour.