Infusion Time¶
Infusion time is how long a bag of IV fluid will take to infuse at a given rate. Knowing infusion time is essential for planning when to hang the next bag, scheduling medications, and documenting expected completion times.
The Basic Relationship¶
This is the same relationship used for flow rate calculations — rearranged to solve for time instead of rate.
Simple Infusion Time¶
Example 1: A 1000 mL bag is running at 125 mL/hr. How long will the bag take to infuse?
Example 2: A 500 mL bag is running at 100 mL/hr. How long will it take?
Converting Decimal Hours to Hours and Minutes¶
When division gives a decimal, convert the decimal portion to minutes by multiplying by 60.
Example 3: A 250 mL bag is running at 75 mL/hr.
Convert the decimal: [0.33 \text{ hr} \times 60 \text{ min/hr} = 20 \text{ min}]
Total infusion time: 3 hours and 20 minutes
Example 4: A 1000 mL bag is running at 150 mL/hr.
Total: 6 hours and 40 minutes
Quick decimal conversions
| Decimal | Minutes |
|---|---|
| 0.25 hr | 15 min |
| 0.33 hr | 20 min |
| 0.5 hr | 30 min |
| 0.67 hr | 40 min |
| 0.75 hr | 45 min |
Remaining Infusion Time¶
When a bag has already been partially infused, calculate remaining time from the remaining volume.
Example 5: A 1000 mL bag was hung at 0800 and is running at 125 mL/hr. It is now 1100. How much time remains?
Volume infused in 3 hours: [125 \text{ mL/hr} \times 3 \text{ hr} = 375 \text{ mL}]
Remaining volume: [1000 \text{ mL} - 375 \text{ mL} = 625 \text{ mL}]
Remaining time: [\frac{625 \text{ mL}}{125 \text{ mL/hr}} = 5 \text{ hr}]
Example 6: A 500 mL bag is running at 100 mL/hr. The bag shows approximately 200 mL remaining. How much time is left?
Calculating Completion Time¶
Add infusion time to the start time to find when the infusion will complete.
Example 7: A 1000 mL bag is hung at 0600 running at 125 mL/hr. When will it finish?
0600 + 8 hr = 1400 (2:00 pm)
Example 8: A 250 mL piggyback is started at 1430 and runs at 75 mL/hr. When will it finish?
1430 + 3 hr 20 min = 1750 (5:50 pm)
Clinical Uses of Infusion Time¶
Why infusion time matters
Knowing when an infusion will complete helps you:
- Plan bag changes — prepare the next bag before the current one runs dry
- Time lab draws — some medications are drawn at trough (just before the next dose)
- Document accurately — nursing notes require expected infusion completion times
- Coordinate medications — some antibiotics must infuse completely before the next dose starts
- Prevent air embolism — know when the bag will run out so you can respond before the line runs dry
Never let an IV run dry
Program the pump's VTBI (volume to be infused) to alert you when the bag nears empty. For critical medications, have the next bag prepared and checked before the current one completes.
Practice Problems¶
Problem 1
A 500 mL bag is running at 125 mL/hr. How long will it take to infuse?
Answer
Problem 2
A 1000 mL bag is running at 83 mL/hr. How long will it take? Express in hours and minutes.
Answer
12 hours and 3 minutes
Problem 3
A 250 mL bag was hung at 0900 and is running at 100 mL/hr. It is now 1100. How many mL remain, and how much longer will it run?
Answer
Volume infused in 2 hours: [100 \text{ mL/hr} \times 2 \text{ hr} = 200 \text{ mL}]
Remaining: [250 - 200 = 50 \text{ mL}]
Time remaining: [\frac{50 \text{ mL}}{100 \text{ mL/hr}} = 0.5 \text{ hr} = 30 \text{ min}]
Problem 4
A 1000 mL bag is started at 2200 and is running at 80 mL/hr. When will it finish?
Answer
2200 + 12 hr 30 min = 1030 the next morning
Problem 5
A 500 mL bag has 325 mL remaining and is running at 150 mL/hr. How much longer will it run?
Answer
2 hours and 10 minutes
Problem 6
Order: 250 mL IV antibiotic piggyback started at 1315, running at 100 mL/hr. Your next assessment is at 1500. Will the bag still be running?
Answer
1315 + 2 hr 30 min = 1545
Yes — the bag will still be running at 1500 with 45 minutes remaining (approximately 75 mL left).