How To Calculate IV Flow Rates

Introduction

Learning how to calculate a basic flow rate is an essential skill for nurses, paramedics and others that are exposed to the administration of intravenous medications. This guide will teach you just that: How to Calculate IV Flow Rates. If you would like to learn how to calculate drip rates, click here.

What is a flow rate?

A flow rate is how fast an IV fluid is administered into a patient. It is important to calculate because different medications are administered at different rates or speeds. If an IV is administered to fast, it can burn the vein, blow the vein or even harm the patient as too much of the medication given too fast can be harmful.

Let’s move onto discussing the formula for how to calculate flow rates.

The Formula

The formula for how to calculate IV flow rates has 3 components.

Volume: The volume is how much liquid is being infused into the patient. The unit for this part of the formula is ALWAYS in millilitres (ml). If your question contains units such as “grams”, its most likely referring to the amount of medication you are giving NOT the amount of fluid. Keep that in mind so you do not get mixed up.

Time: The time for flow rate questions is how long the infusion is going to take. The unit for this is ALWAYS in hours.

Flow Rate: The flow rate is the outcome of calculating a flow rate (obviously). It is how fast the fluid is being put into the patient. The unit for this is ALWAYS in ml/hour.

The formula for how to calculate an IV flow rate is the following: Lets go through a practice questions and apply this formula.

Practice Question

Step One: Identify The 2 Required Variables

Remember, the formula has 3 variables, one of which you are trying to solve for (obviously flow rates). The two you need to identify are Volume and Time.

Volume: It is important to remember that the volume is how much fluid is entering this individual. This question contains a quantity of medication but don’t let that throw you off. The volume in this question is stated as “50ml”. If the volume was in liters instead, you would have to convert to millilitres.

Time: The time is given to you in this question and it is “30 minutes”. This is a problem because if you look at the formula, the time MUST BE IN HOURS. You must now convert 30 minutes into hours. To do this you must divide by 60 minutes (because there are 60 minutes in an hour).

30/60 = 0.5 hours

Step Two: Fill In The Equation

Once you have identified time and volume, put them into the formula. It should look like this: Step 3: Solve The Equation

50/0.5= 100 ml/hour. The units for flow rates are always ml/hour. If you do not have ml and hours in your question, you have done something wrong.

TIP: Never forget the units on a test or quiz, instructor and professors will most likely deduct marks.

Congratulations, you now know how to calculate IV Flow Rates!

Try these practice questions to test your knowledge:

1. A patient requires an antibiotic in 30 mL D5W over 15 minutes. What is the flow rate in ml/hour?

2. You need to infuse 1.8 L of NS to infuse over 15 hours. What is the flow rate in ml/hour?

3. Order: 1500 mL of NS over 12 hours. What is the flow rate in ml/hour?

4. What is the flow rate in ml/hour required needed to infuse 750ml of 5D1/2S in 5 hours?

5. You have orders to infuse 50mg of Chloramphenicol in 100 ml of 5% Dextrose in Water over 30 minutes. What is the correct rate of flow in ml per hour?

6. Infuse 500 ml of 5% Dextrose in Normal Saline over 4 hours. Add 10 MEq of KCl to solution. What is the correct flow rate in ml/hour?

7. The doctor orders 1.5 liters of normal saline solution to be administered intravenously to your patient over the next 12 hours. What is the flow rate in ml/hour?

8. Cirpo in a 50 ml bag needs to be infused in 15 minutes. What do you set the flow rate to in ml/hour?

9. A 100ml bolus of saline needs to be infused in 20 minutes, how fast do you set the flow rate?

10. 450 ml of NS needs to be infused in 45 minutes. What does the flow rate need to be in ml/hour?