How to calculate heparin drip rate

Heparin is a very effective anticoagulant that is used frequently in hospitals. One way to administer Heparin is through an intravenous (IV) drip. It is essential to calculate the dosage of Heparin properly, since too much or too little can be harmful and even potentially deadly. If the physician has prescribed a specific number of Heparin units per hour for the patient, you will need to calculate the drip rate that will obtain the proper dosage.

Verify the number of Heparin units in the IV bag and the volume of fluid in the bag.

Divide the number of units of Heparin in the IV bag by the number of millilitres of fluid in the bag to get the number of units per millilitre. For example, for a 1-liter (1,000-milliliter) bag of D5W with 40,000 units of Heparin, 40,000 ÷ 1,000 = 40. Therefore, the IV bag has a concentration of 40 units per millilitre (U/ml) of Heparin.

Verify the number of units of Heparin per hour the physician has prescribed.

Divide the number of units per hour that the physician prescribed for the patient by the number of units of Heparin per millilitre of IV solution. For example, if the physician prescribed 880 units per hour of Heparin, and the IV bag has a concentration of 40 units per millilitre, then 880 ÷ 40 = 22. Therefore, the drip rate for the IV should be 22 millilitres per hour.


Remembering that 1 litre = 1,000 millilitres makes it very easy to calculate the number of units in a 1-liter IV bag. For a smaller bag, it's best to use a calculator.


Be sure to always double-check the volume of the IV bag and the number of Heparin units. If you have an incorrect number for either of these, it could lead to a potentially harmful miscalculation.

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About the Author

Melissa Sandoval began writing professionally in 1996, dabbling in fiction and writing for new media and magazines. She has published work in "mental_floss magazine" and on websites such as TLC Family and TLC Style. Sandoval has work published in English and Spanish, including online topics guides en Español. Sandoval has a Bachelor of Arts in psychology from Wittenberg University.