Heparin drip Nomogram for Acute Coronary Syndrome/Atrial Fibrillation

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The purpose of this guideline is to provide dosing assistance for unfractionated heparin therapy for the treatment of acute coronary syndrome (ACS) or atrial fibrillation (AF) based on anti-factor Xa values (calibrated for heparin).

University of Michigan Health System Anticoagulation Program

Guideline for Managing Unfractionated Heparin for Treatment of Acute Coronary Syndrome or Atrial Fibrillation in Adult Patients Based upon Anti-Factor Xa Levels

Initial Dosing and Dosage Adjustments

Heparin should be dosed based upon actual body weight (kg): ____

  1. Bolus doses (round to nearest 10 units)

Note: DO NOT exceed the following initial bolus limits:

  • ST-segment elevation MI treated with tPA, maximum bolus = 4,000 units
  • Unstable angina or non-ST-segment elevation MI, maximum bolus = 5,000 units
    • Initial bolus dose 60 units/kg
    • Other initial bolus: _______ units/kg
    • No initial bolus
    • No bolus EVER
  1. Continuous infusion rate (round to nearest 10 units)

For unstable angina, non-ST-segment elevation MI or ST-segment elevation MI treated with tPA do not exceed maximum initial rate of 1,000 units/hour.

  • Initiate infusion at 12 units/kg/h
  • Other initial infusion rate : _________ units/kg/h
  • Non-weight based initial infusion rate : _________ units/h
  1. Monitoring
  • Draw INR/PT, CBC with platelet count and aPTT prior to starting heparin
  • Draw STAT anti-factor Xa 6 hours after starting heparin
  • Monitor anti-factor Xa and adjust per Weight-Adjusted Heparin Nomogram (target anti-factor Xa 0.2-0.5 units/mL)
  • Platelet count should be monitored daily for a minimum of 2 weeks and hemoglobin/hematocrit at least weekly

Weight-Adjusted Heparin Nomogram



Repeat Heparin

Bolus Dose

Hold Infusion


Rate Change

Repeat Anti-Xa level

Less than 0.1*

70 units/kg†


Increase 1.5 units/kg/h

6 hours


40 units/kg†


Increase 1 units/kg/h

6 hours




No change

6 hours**




Decrease 1 units/kg/h

6 hours



30 min

Decrease 1.5 units/kg/h

6 hours

Greater than or equal to 0.9*


60 min

Decrease 2 units/kg/h

6 hours

*Notify physician if 2 consecutive Anti-Xa values are in this range

**When 2 consecutive Anti-Xa values are in therapeutic range (0.2-0.5 units/mL), obtain Anti-Xa assay the next morning and every 24 hours thereafter

† Please ensure physician has not selected “No bolus ever” option above

Special Thanks


If reusing this content please use the following information to provide credit to the content authors:  

  1. Title: Heparin drip Nomogram for Acute Coronary Syndrome/Atrial Fibrillation
  2. Author:  Michigan Medicine
  3. Source: https://ecosystem.tactuum.com/
  4. License: “CC BY-NC 4.0”

Heparin drip Nomogram for Acute Coronary Syndrome/Atrial Fibrillation,  Michigan Medicine, Dept of Surgery,  “CC BY-NC 4.0”

Last reviewed: 09 June 2021