Unit 10: Intravenous (IV) Flow Rate Calculations

10.1 Overview

Nurses are responsible for ensuring that patients are receiving the correct intravenous fluid flow rate. Flow rates are administered at rates expressed in milliliters per hour (mL/hr).

10.2 Learning Outcomes

After completing this unit, you will be able to

SAFETY ALERT!  The usual flow rate in milliliters per hour ranges from 50 to 200 mL per hour (Gray Morris & Brown, 2017, p. 530). If the flow rate you have calculated exceeds this amount, always double-check the order and your calculation.

10.3 Learning Resources

The following resources will assist you in achieving the learning outcomes for this unit. If a resource link does not function, use a search engine to locate the current link and alterative websites.

Buchholtz, S. (2016). Henke’s med-math: Dosage calculation, preparation, and administration (8th ed.). Philadelphia, PA: Wolters Kluwer.

Diehl-Oplinger. (n.d.)
Brush up on your drug calculation skills. https://studylib.net/doc/8571859/brush-up-on-your-drug-calculation-skills

DosageHelp. (2018). Vol/time – IV drop rate questions. Retrieved from http://www.dosagehelp.com/iv_rate_drop.html

Gray Morris, D.C., & Brown, M. (2017). Calculate with confidence (1st Canadian ed.). Toronto: Elsevier Canada. 

Olsen, J.C., Giangrasso, A. D., & Shrimpton, D. (2016). Medical dosage calculations a dimensional analysis approach (11th ed.). New Jersey:Pearson Education.

RegisteredNurseRN. (2015). Calculations for nursing students on IV drip rate factors made easy [Video File]. Retrieved from https://www.youtube.com/watch?v=W5VIc6f0fBA

RegisteredNurseRN. (2015). Dosage calculations for nursing students on IV drip rate factors made easy (video 4) [Video File]. Retrieved from https://www.youtube.com/watch?v=W5VIc6f0fBA

RegisteredNurseRN. (2018). How to solve IV drug dosage problems with dimensional analysis. Retrieved from http://www.registerednursern.com/how-to-solve-iv-drug-dosage-problems-with-dimensional-analysis/

RegisteredNurseRN. (2018). IV infusion time practice problems. Retrieved from http://www.registerednursern.com/iv-infusion-time-practice-problems/

RegisteredNurseRN. (2018). Quiz IV: Flow rate drip factors practice questions. Retrieved from http://www.registerednursern.com/quiz-iv-flow-rate-drip-factors-practice-questions/

RegisteredNurseRN. (2018). Quiz IV: Infusion rates practice questions mL/hr. Retrieved from http://www.registerednursern.com/quiz-iv-infusion-rates-practice-questions-mlhr/

Wilson, K. (2013). The nurse’s quick guide to I.V. drug calculations. Nursing Made Incredibly Easy, 11(2), 1-2. Retrieved from https://journals.lww.com/nursingmadeincrediblyeasy/...  doi10.1097/01.NME.0000426306.10980.65

10.4 Learning Activities

1. Review Buchholtz (2016) Chapter 6 Power Point presentation.

2. Calculating the following IV flow rates in mL/hr. 

500mL in 12 hr =

42 mL/hr
500 mL divided by 12 hours equals 42 mL/hr

1000 mL in 4 hr =

250 mL/hr
1000 mL divided by 4 hours equals 250 mL/hr

750 mL in 2.5 hr =

300 mL/hr
750 mL divided by 2.5 hours equals 300 mL/hr

4 mg IV in 250 mL D5W in 1 hour =

250 mL/hr
250 mL divided by 1 hour equals 250 mL/hr

500 mL D5RL in 24 hr =

21 mL/hr
500 mL divided by 24 hours equals 21 mL/hr

25 mg of Ondansetron in 100 mL to infuse over 1 hour =

100 mL/hr

Ampicillin 750 mg IV in 250 mL of NS to infuse over 2.5 hours =

100 mL/hr

The prescriber orders 1000 mL to be infused over 24 hours. What will you record as intake after your eight-hour shift? Round answer to whole number.

333 mL
1000 mL divided by 24 hours equals 41.66 mL per hour.
41.66 mL multiplied by 8 hours equals 333.28 mL.
Rounded to 333 mL

The prescriber orders 1000 mL to be infused from 0800 to 2000. At what rate in mL/hr will you set the pump?

83 mL/hr
1000 mL divided by 12 hours equals 83 mL/hr

3. When a medication is added to a small fluid volume and ordered to infuse in less than an hour, the flow rate is still calculated in mL/hr.

X mL/h = total mL to infuse  x 60 min/hr
               # of minutes
Calculate the following IV flow rates in mL/hr.

Cefazolin 500 mg in 50 mL NS over 30 minutes =

100 mL/hr
50 mL x 60 min = 100 mL/hr 30 mins     hr
Didn’t understand how to calculate this question? Watch this video on how to solve this question using dimensional analysis!

Ampicillin 750 mg IV in 30 mL NS over 20 minutes =

90 mL/hr
30 mL x 60 min = 90 mL/hr
20 mins    hr

Ceftizoxime 500 mg IV in 50 mL NS over 15 minutes =

200 mL/hr
50 mL x 60 min = 200 mL/hr
15 mins    hr

Ceftriaxone 1500 mg IV in 100 mL over 45 minutes =

133 mL/hr
100 mL x 60 min = 133 mL/hr
45 mins    hr

Ondansetron 4 mg IV in 50 mL D5W over 15 minutes =

200 mL/hr
50 mL x 60 min = 200 mL/hr
15 mins    hr

4. When a pump is not used, the nurse must manually regulate the IV flow rate by calculating the rate as the number of drops per minute (gtts/min). The drop factor is regulated by the size of the tubing (the larger the tubing the larger the drops). The macrodrop is the standard type of tubing used for general IV administration. Macrodrop tubing delivers 10, 15, or 20 drops equal to 1 mL (Gray Morris & Brown, 2017). Always read the tubing package to identify the drop factor of the tubing.

X gtts/min = amount of solution (ml) x drop factor (gtts/mL)
                               time (min)

Practice calculating the drop factor in drops per milliliters.

Infuse D5W to at the rate 100 mL/hr. The drop factor is 10 gtts/mL. What flow rate in drops per minute should be regulated?

17 gtts/min
Solve for gtts/min
100mL x 10 gtts x 1 Hr = 17 gtts/min
 Hr              mL      60 mins

Infuse IV medication in 50 mL NS in 20 minutes. The drop factor is 60 gtts/mL. What flow rate (in drops per minute) should the IV be set?

150 gtts/min
Solve for gtts/min
50mL x 60 gtts = 150 gtts/min
20 mins          mL

Administer D5W at 75 mL/hr with a drop factor of 10 gtts/mL

13 gtts/min
Solve for gtts/min
75 mL x 10 gtts x 1 hr = 13 gtts/min
 Hr              mL      60 mins

Administer Ringers lactate (RL) at 125 mL/hr using a drop factor of 15 gtts/mL

31 gtts/min
125 mL x 15 gtts x 1 hr = 31 gtts/min
 Hr              mL      60 mins

Administer 1 000 mL D5 0.33% NS in 6 hours. The drop factor is 15 gtts/min.

42 gtts/min
1000 mL x 15 gtts x 1 hr = 42 gtts/min
 6 Hrs           mL      60 mins

5. Apply your learning by working on the following case study: 

A 68-year-old male is admitted to hospital. His skin is clammy, and he has a decreased level of consciousness. He is allergic to aspirin and penicillin. He has a history of hypertension, Type 2 diabetes, COPD, osteoarthritis, and CHF. He had a right-sided CVA 10 years ago, is aphasic, and has right sided hemiplegia. He is 5 foot 3 inches and weighs 140 lbs. His vital signs are: T 36.3, BP 100/60, P 100, R 26 and shallow. His admitting diagnosis is dehydration, R/O pneumonia, UTI, and sepsis. 

The prescriber orders include the following:

You initiate a 1000 mL bag of NS @ 0800. What time of day using 2400 clock will the full bag be fully infused?

1900 hr
1000mL/ 90mL = 11.11 hr
0800h + 11 hr = 1900h

You don’t have a pump so you must hang the bag by gravity. How many drops per minute will you calculate to run as per order?

15 gtts/min
90 mL/hr divided by 60 minutes per hour equals 1.5 mL per minute.
1.5 mL per minute multiplied by 10 drop factor equals 15 drops per minute
90mL x 10 gtts x 1 hr/60 mins = 15 gtts/min Hr          mL        60 mins

The parenteral monograph tells you to reconstitute the 1500 mg of Ceftriaxone in 100 mL of NS and to run over 30 minutes. What will you set the secondary rate at so that the drug is infused in the proper time?

200 mL/hr
100 mL x 60 mins/hr = 200 mL/hr
30 mins

6. Nurses must frequently monitor and check IV flow rates. Rates change when a patient stands, sits, or repositions him or herself in bed if IVs infuse by gravity.  Before making any kind of change, always assess the patient.  “A safe rule is that the recalculated flow rate should not vary from the original flow rate by more than 25%. If the calculated flow rate varies by more than 25% from the original flow rate, the prescriber should be notified” (Gray Morris & Brown, 2017, p. 566).

X mL/hr = remaining volume (mL)/ Remaining time (hr)

Determine whether the new rate is greater or less 25% (use the amount of increase or decrease divided by the original flow rate).

Amount of increase or decrease =  % of variation of original rate (nearest whole %)

Original IV rate was 1000 mL of NS was to infuse in 8 hours at 125 mL/hr.  However, after 4 hours, you notice 700 mL of fluid left in the IV.

With a rate of 125 mL/hr how much fluid should have infused after 4 hours?

500 mL
125 mL x 4 hrs = 500 mL hr

Recalculate the IV flow rate so that the 1000 mL will be infused within the original 8 hours. What will the new flow rate be?

175 mL/hr
4 hrs remaining, total volume left Is 700 mL
700 mL / 4hrs = 175; = 175 mL/hr

Determine the percentage of change.

40%
175 – 125 / 125 mL = 50/125 = 0.4 or 40%

Is the percentage of change > or < than 25%?

greater

What are your initial actions?

Assess the patient status and if they can safely tolerate this new rate. If yes, call the doctor for a new rate.

7.  Calculate the following changes in IV flow rates.

An IV of 1000 mL NS is to infuse from 0700 to 1500 (8hr) at a flow rate of at 125 mL/hr. In 5 hours, you notice that 700 mL has infused. Recalculate the flow rate for the remaining solution so that it still infuses in 8 hours.

100 mL/hr
Remaining time is 3 hrs, and remaining volume is 1000mL – 700mL = 300 mL
300 mL / 3hr = 100 mL/hr

Determine the percentage of change.

- 20%
100 – 125 / 125 = -25 / 125 = -0.2 or -20%

500 mL of 0.9% NS was to infuse in 8 hr at 63 mL/hr. After 5 hours, you find 250 mL of fluid left. How do you proceed?

Remaining volume is (500mL – 250mL = 250 mL); remaining time is (8hrs – 5 hrs = 3 hrs)
250 mL/ 3 hr = 83 mL/hr
83 – 63 / 63 = 20/63 = 0.317 = 32%
Assess patient then get new order

250 mL of D5W was to infuse in 3 hours at 83 mL/hr. With 1 ½ hours remaining, you find 200 mL of the solution is remaining. How do you proceed?

Remaining volume is 200 mL, remaining time is 3hr – 1.5 hr = 1.5hr
200 mL/1.5hr = 133 mL/hr
133 – 83 / 83 = 50/83 = 0.61 = 61%
Assess patient then get new order

1500 mL of 2/3 1/3 NS was to infuse in 12 hours @ 125 mL/hr. After 6 hours, 650 mL was infused. How do you proceed?

Remaining volume (1500mL – 650mL = 850mL); remaining time is 12hrs – 6 hrs = 6 hrs)
850mL/6h = 142 mL/hr
142 – 125 / 125 = 0.136 or 14%
This is an acceptable increase. Still assess patient and change flow rate if patient can tolerate.

See an explanation video here.

10.5 Self-Evaluation Exam

When you think you have your IV calculations mastered. Evaluation yourself ~ take this exam and aim to achieve 100%

http://www.registerednursern.com/quiz-iv-flow-rate-drip-factors-practice-questions/

http://www.registerednursern.com/iv-infusion-time-practice-problems/

http://www.registerednursern.com/quiz-iv-infusion-rates-practice-questions-mlhr/

10.6 Reflection

Gray Morris and Brown (2017, p. 510) state that nurses need to know that fluids administered directly into the bloodstream have a rapid effect. This is necessary during emergencies or other critical care situation when medications are required. However, IV administration of medication can be rapidly fatal to the patient if the incorrect medication or dosage is administered.

Last updated: April 11, 2022 © Copyright Athabasca University
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