How to Calculate a Heparin Bolus

Updated July 20, 2017

Heparin is a drug which helps to prevent the formation of blood clots in blood vessels. Its primary function is to thin the blood and it is the primary treatment for conditions which may lead to heart failure. Using Heparin, however, is a difficult process which requires knowledge of the drug and close monitoring of the recipient's age, weight, bleeding time, etc. Using the drug without the proper knowledge or calculations can result in either under-dosing or overdosing. Both scenarios can lead to serious health-related complications.

Use the measuring tape to ascertain the patient's height in inches. Use the patient's height to calculate his or her ideal body weight. For men, subtract 60 from the height and multiply the result by 2.3 and add 50 to obtain the result. For females, subtract 60 from the height and multiply the result by 2.3 and add 45. The formula described is given below:

Men = 50 + 2.3 ([Height in inches] - 60)

Women = 45.5 + 2.3 ([Height in inches] - 60)

Divide the patient's current weight by the ideal body weight and multiply it by 100. If the result is above 140%, the patient is considered obese, and you should subtract the ideal weight from the current weight and multiply it by 0.4. The result is then added to the ideal body weight and this value is used to calculate the bolus. In non-obese patients the current weight is used as the dosing weight.

Multiply the standard heparin bolus dosage (80 Units/Kg) with the dosing weight, if the patient is under age 70. If the patient's age is over 70, use 50 Units/Kg as a standard and multiply it to the dosing weight. Round the result and ensure that the dosage does not exceed 10,000 units.

Patient Under 70 = 80U/Kg X Dosing Weight (Kg)

Patient Over 70 = 50U/Kg X Dosing Weight (Kg)

Divide the number of units calculated with 1000 to calculate the number of millilitres to administer as the bolus.

Calculated Dose/1000 (U/ml) = Bolus dose in ml/hr.

Start the Heparin IV at the calculated dose and administer a maintenance dose every hour. This is calculated by:

18(U/Kg) X Dosing Weight

This is then rounded to the nearest 40U and then divided by 1000U/ml.


Repeat the Blood CP test to obtain the patient's PTT six hours after the initial IV bolus has been administered. Once the PTT is in the 70 to 100 second range, the bolus dose is discontinued in favour of the maintenance dose. If the therapeutic time shown above is not attained, the bolus is recalculated using the current PTT or the Heparin response curve.


Dispose of all syringes, IV and cannula appropriately after single use. Do not inject the bolus directly into muscle, rather inject it into a vein.

Things You'll Need

  • Heparin IV
  • Weighing scale (KG)
  • Measuring tape
  • Blood panel showing PTT (partial thromboplastin time) and platelet count
  • Calculator
  • IV and cannula set
  • Internet connection
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About the Author

Mahmood Shaikh started writing in 2009 as a research writer at the Niatah Corp. His work has been published in "Students Spectrum Magazine." He holds a bachelor's degree in medicine from Dow University of Health Sciences in Karachi, Pakistan.