If 1000 mL normal saline is to be infused over 12 hours with a drop factor of 15 gtt/mL, what is the flow rate in drops per minute?

If 1000 mL normal saline is to be infused over 12 hours with a drop factor of 15 gtt/mL, what is the flow rate in drops per minute?

• A. 16 gtt/min
• B. 21 gtt/min
• C. 28 gtt/min
• D. 32 gtt/min

Answer: (B)

The main idea is to convert everything to compatible units and use the drops-per-minute formula: flow rate (gtt/min) = (volume in mL) × (drop factor in gtt/mL) ÷ (time in minutes). Here, 1000 mL is to be infused over 12 hours. Convert hours to minutes: 12 × 60 = 720 minutes. Multiply volume by drop factor: 1000 × 15 = 15000 drops total. Now divide by the infusion time: 15000 ÷ 720 ≈ 20.83 gtt/min. Since you can’t have a fraction of a drop, round to the nearest whole drop, giving 21 gtt/min.

The main idea is to convert everything to compatible units and use the drops-per-minute formula: flow rate (gtt/min) = (volume in mL) × (drop factor in gtt/mL) ÷ (time in minutes).

Here, 1000 mL is to be infused over 12 hours. Convert hours to minutes: 12 × 60 = 720 minutes. Multiply volume by drop factor: 1000 × 15 = 15000 drops total. Now divide by the infusion time: 15000 ÷ 720 ≈ 20.83 gtt/min. Since you can’t have a fraction of a drop, round to the nearest whole drop, giving 21 gtt/min.