Free Tool
Heparin Drip Rate Calculator (mL/hr)
Convert a heparin units-per-hour order to a pump rate in mL/hr.
Formula
mL/hr = (ordered units/hr × bag volume in mL) ÷ total units in bag
e.g. 25,000 units in 250 mL
e.g. 25,000 units in 250 mL → enter 250
Result
Enter values above to calculate.
Worked example
Scenario: Order: Heparin infusion at 1,200 units/hr. Bag concentration: 25,000 units in 250 mL D5W.
- 1Identify ordered rate (1,200 units/hr) and bag concentration (25,000 units per 250 mL).
- 2Apply formula: (1,200 × 250) ÷ 25,000 = 300,000 ÷ 25,000 = 12.
Set the pump to 12 mL/hr.
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When to use this calculation
Heparin is a high-alert medication — small dose errors cause major bleeding or thrombosis. Heparin orders are almost always written in units (units/hr for maintenance, units/kg/hr for weight-based, units as a bolus), but infusion pumps run in mL/hr. This calculation converts the order to a pump-ready rate based on the bag's concentration. Always require an independent double-check from a second licensed nurse before programming the pump.
Bag concentrations vary by institution (common: 25,000 units in 250 mL, or 25,000 in 500 mL). Read the bag label every time — assuming the concentration is a near-miss waiting to happen. After programming the rate, verify the aPTT or anti-Xa per protocol and adjust per the institution's heparin titration nomogram; never adjust based on calculation alone.