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Dosage Calculations

Beginning Intravenous Therapy

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Flow Rate

Order usually as mL/hr or set amount over a

given length of time

Examples:

20 mL/hr or 125 mL/hr

500 mL over 10 hours

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Flow Rate

Calibration factors vary

Minidrop set is always 60 gtts/ml

Macrodrop set can be 10gtts/mL, 12gtts/mL, 15gtts/mL, or

20gtts/mL

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Flow Rate

Formula

Total mL (per hour) X drop factor

time in minutes (if per hour amt = 60)

Your answer is always labeled gtts/min

**note gtts/min is always rounded to a

whole number***

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Flow Rate Example One:

125 mL is ordered to infuse over 30 minutes

using a calibration factor of 12 gtts/mL,

calculate the flow rate.

125 mL X 12 gtts/mL = 50 gtts/min

30 minutes

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Flow Rate Example Two:

250 mL is ordered to infuse over 6 hours.

Calculate the flow rate using a microdrop

set.

First find the mL/hr to be infused

Then plug information into the formula

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Flow Rate Example Two:

250 ml to infuse over 6 hours

mL = mL/hr

hr

250 mL = 41.6 mL/hr

6 hrs

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Flow Rate Example Two:

41.6 mL/hr X 60 gtts/mL = 41.6

60 minutes

41.6 rounds to 42 gtts/min

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Flow Rate Example Using dimensional

Anaylsis: 500 mL NS is ordered to infuse over 5 hours.Find the flow rate using 10gtts/mL drop factor.

500 mL X 1hr X 10 gtts = 60 gtts/min

5 hrs 60 min 1 mL

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Re-timingF

low Rate Sometimes IVs will infuse slower or faster

than desired and the nurse will need to

adjust the rate to complete the IV on time.

NOTE: if an increase in rate is required

assess your patient to make sure they cantolerate the increase vascular fluids

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Re-timingF

low Rate You will use the flow rate formula

Find the mls left and time left for the

infusion and use these numbers

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Re-timingF

low Rate Example: An IV of 250 mL over 6 hours

has been infusing for 2 hours. How ever,

100 cc has already infused and thereforeinfusing too fast. Re-time the flow rate tocomplete this infusion on time using a 10gtts/mL factor.

Time left = 4 hours

Fluid left = 150 mL

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Re-timingF

low Rate Find mL/hr

150 mL left = (37.5 mL/hr

4 hours left

37.5 mL/hr X 10 gtts/mL = 6.25

60 minutes

6.25 = 6 gtts/min

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Calculating IV rate from flow

rate

Example: An IV running @ 20 gtts/min has

a drop factor of 20 gtts/mL. How many

ml/hr will the patient receive?

Start with flow rate

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Calculating IV rate from flow

rate20 gtts X 60 min = 1200gtts

min hr

1200 gtts divided by 20gtts (drop factor)

hr

gives 60 mL/hr

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Calculating IV rate from flow

rate Example: An IV of 0.45 NS is infusing at

30 gtts/min. Using a microdrip set calculate

the infusion rate.

30 gtts/min X 60min = 1800 gtts/hr

1800 gtts/hr = 30 mL/hr

60 gtts/mL

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Can Also Use Flow Rate Formula

Example: An IV of 0.45 NS is infusing at

30 gtts/min. Using a microdrip set calculate

the infusion rate.

?mL/h x 60 gtt/mL = 30 gtt/min

60 minutes

X = 30 mL/h