Intravenous flow rates

When a provider orders an intravenous infusion, it is your responsibility to make sure that the fluid will infuse at the prescribed rate. IV fluids may be infused by gravity using manual control or infused using an infusion pump. Regardless of the method, you will be responsible for calculating the correct IV flow rate.

How to calculate IV flow rates

The infusion flow rates refers to the amount of drops per minute needed to infuse a volume of IV fluid in a certain amount of time with micro drip tubing.

The IV micro drip rate is calculated according to the volume of IV fluid that needs to be infused, the drop factor of micro drip tubing which is 60 drops per minute (60 gtt/min), and the amount of time that the fluid is infused.

For IV driprate calculation, we need the following inputs :

1. Volume

The volume of fluid is the volume of fluid that needs to be infused in the period of time specified in the time variable into the person.

2. Tubing drop factor

The drop factor, also called the drip factor, is the calibration or number of drops per mL of solution delivered for a particular drip chamber. Always check the tubing package to be sure. Microdrip tubing universally delivers 60 gtt/mL. It is used for infusing small or very precise amounts of fluids. The most common values are 10 drops per mL or 15 drops per mL.

3. Time duration

The time is the period of time which we want to infuse the IV fluid into the person.The time is always specified in minutes when we are dealing with drops. Because drops are always calculated in drops per minute. When we are dealing with infusion with milliliters (mL), we calculate that rate in milliliters per hour (mL/hr). When we are dealing with drops, we calculate in drops per minute.

Formula used :

Once we have the volume of fluid we are infusing and the time that we are going to infuse it in, we calculate the IV drip rate according to the formula,

IV drip rate (gtt/min)= (Volume (ml) / Time(mins) * DropFactor.

This will give us the answer in drops per minute (gtt/min).

And using below formula, we determine how many mL/hr to set the IV pump to deliver.

IV drip rate (ml/hr) = (IV drip rate (gtt/min)/ DropFactor ) * (60 min/ 1 hr))

Example: The provider has ordered ranitidine (Zantac) 50 mg in 100 mL 0.9% sodium chloride intravenous piggyback to be infused over 20 min. You have a macrodrip tubing with a drop factor of 10 gtt/mL. Calculate how many gtt/min to set as the IV flow rate.

Using Formula :

IV driprate(gtt/min) = ( 100 ml / 20 mins ) * 10 = 50 drops per minute

IV driprate(ml/hr) = (50 dpm / 10 dpml)* (60 min/1 hr) = 300 millilitre per hour

When calculating the flow rate, first determine whether the intravenous tubing you are using is microdrip or macrodrip, so that you can use the appropriate drop factor in your calculations. The drop factor, also called the drip factor, is the calibration or number of drops per mL of solution delivered for a particular drip chamber. Always check the tubing package to be sure. Microdrip tubing universally delivers 60 gtt/mL. It is used for infusing small or very precise amounts of fluids. Macrodrip tubing varies with the manufacturer but usually delivers between 10 gtt/mL and 15 gtt/mL. It is used to infuse large volumes or to infuse fluids quickly.

If you are looking for an apt app which makes these calculations simpler and easy to use, please download "Driprate Pro" app, developed by Codemagma, from Apple play store and google play store available for free. This app is thoughtfully designed to helps you avoid complex manual calculations to get desired Intravenous (IV) drip rate of Infusion.Calculate drips per minute easily with simple IV inputs. It allows the user to set alert notifications, which will notify user, 15 mins prior to the completion of infusion. Also, It allows user to save the details of the patient, along with the medicine and infusion completion time.