Heparin Infusion Rate Calculator

Patient Weight (kg)

Desired Dose (units/kg/hr)

Total Heparin in Bag (units)

Bag Volume (mL)

Calculation Results

Total Dose per Hour: —

Concentration: —

Infusion Rate: —

Understanding Heparin Infusion Rate Calculations

Heparin is a critical anticoagulant used in clinical settings to prevent and treat thromboembolic events such as deep vein thrombosis (DVT) and pulmonary embolism. Because heparin has a narrow therapeutic window, calculating the precise infusion rate in milliliters per hour (mL/hr) is essential for patient safety.

The Heparin Calculation Formula

To determine the infusion rate, you must first calculate the total units required per hour and then relate that to the concentration of the IV bag. The standard formula used by this calculator is:

Step 1: Total Units/hr = Dose (units/kg/hr) × Patient Weight (kg)
Step 2: Concentration (units/mL) = Total Units in Bag / Bag Volume (mL)
Step 3: Infusion Rate (mL/hr) = Total Units per Hour / Concentration

Real-World Example Calculation

Imagine a patient weighing 80 kg who is ordered a Heparin drip at 18 units/kg/hr. The pharmacy provides a standard bag of 25,000 units of Heparin in 250 mL of D5W.

Step 1: 18 units/kg/hr × 80 kg = 1,440 units/hr
Step 2: 25,000 units / 250 mL = 100 units/mL
Step 3: 1,440 units/hr ÷ 100 units/mL = 14.4 mL/hr

The infusion pump would be set to 14.4 mL/hr to deliver the prescribed dose.

Clinical Importance of Accuracy

Inaccurate dosing of heparin can lead to severe complications. Under-dosing may result in the failure to treat or prevent clots, while over-dosing significantly increases the risk of major bleeding. Always verify infusion rates with a second clinician per institutional protocol. This tool serves as a reference and should not replace clinical judgment or institutional weight-based heparin protocols.

function calculateHeparinRate() { var weight = parseFloat(document.getElementById('calc_weight').value); var doseKg = parseFloat(document.getElementById('calc_dose').value); var totalUnits = parseFloat(document.getElementById('calc_total_units').value); var bagVolume = parseFloat(document.getElementById('calc_bag_volume').value); // Validation if (isNaN(weight) || weight <= 0 || isNaN(doseKg) || doseKg <= 0 || isNaN(totalUnits) || totalUnits <= 0 || isNaN(bagVolume) || bagVolume <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // Calculation Logic var totalUnitsPerHour = doseKg * weight; var concentration = totalUnits / bagVolume; var mlPerHour = totalUnitsPerHour / concentration; // Displaying Results document.getElementById('res_units_hr').innerText = totalUnitsPerHour.toLocaleString() + " units/hr"; document.getElementById('res_concentration').innerText = concentration.toFixed(2) + " units/mL"; document.getElementById('res_ml_hr').innerText = mlPerHour.toFixed(1) + " mL/hr"; // Show result container document.getElementById('heparin_results').style.display = 'block'; }