Intravenous (IV) Calculations_ Gtt_min, mL_hr, Units_hr & mcg_kg_min

INTRAVENOUS CALCULATIONS
This unit covers how to calculate gtt/min, mL/hr, units/hr, and mcg/kg/min medication problems.

Drops Per Minute (gtt/min) Calculations

MEMORIZE THIS
Drops = gtt
Drop Factor = gtt/mL
Drop Rate = gtt/min
Microdrip set = 60gtt/mL
1 hour = 60 minutes

The intravenous (IV) catheter set is calibrated to deliver a certain amount of drops per 1 mL, known as the drop
factor.

A macrodrip tubing set will deliver 10, 15, or 20 gtt/mL, which is typically used for adult intravenous
administrations. A microdrip tubing set will deliver 60 gtt/mL which is used more in pediatrics or critical care
settings.

The gtt/mL (drop factor) will be printed on the intravenous tubing set

Example Problem:
The order is to infuse 125 mL/hr. The drop factor is 10 gtt/mL.
How many gtt/min will infuse?
Step 1:
Write the unit of measure being calculated. We are looking for 2 units of measurement in this problem.

gtt =
min

Step 2:
The numerator of what you are solving for must go in the first numerator spot of the problem. Remember, keep
your “sisters” together and place the other part of the ratio in the denominator spot.

gtt = 10 gtt
min 1 mL

Step 3:
Now, follow the leader diagonally with matching units of measurement. Then convert using the time
conversion 1 hour = 60 minutes, if minutes is not in the last denominator spot.

gtt = 10 gtt x 125 mL x 1 hr =
min 1 mL 1 hr 60 min

Step 4:
Cross out matching units of measurement. You should have gtt/min remaining. Now, calculate. Round to the
whole number. You cannot have an accurate half of a drop.

gtt = 10 gtt x 125 mL x 1 hr = 1250 = 20.8 = 21 gtt/min
min 1mL 1hr 60 min 60
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, Example Problem:
The order states to infuse 90 mL/hr with a drop factor of 20 gtt/mL. Calculate the gtt/min.

gtt = 20gtt x 90mL x 1hr = 1800 = 30 gtt/min
min 1mL 1hr 60min 60

Example Problem:
Administer 80 mL/hr using a 15 gtt/mL set. How many gtt/min will be delivered?

gtt = 15gtt x 80mL x 1hr = 1200 = 20 gtt/min
min 1mL 1hr 60min 60


PRACTICE EXERCISE #1

1. Administer 110 mL/hr using a drop factor of 20 gtt/mL. What are the gtt/min? Round the answer to the
nearest whole number.




2. An IV of 1000 mL is ordered to infuse at 150 mL/hr using a 10 gtt/mL set. What are the gtt/min? Round the
answer to the nearest whole number.




3. A medication volume of 50 mL is to infuse at 20 mL/hr using a 20 gtt/mL set. Calculate the gtt/min. Round
the answer to the nearest whole number.




4. A rate of 60 mL/hr is ordered for a volume of 250 mL using a drop factor of 10 gtt/mL. Calculate the
gtt/min. Round the answer to the nearest whole number.




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