mL/hr (Milliliters per Hour): IV Flow Rate Explained
Shows the work. Every example is computed with the formula and numbered steps. For study and exam practice, not for patient care.
mL/hr: Milliliters per hour: the flow rate an infusion pump is programmed in.
mL/hr is a flow rate: how many milliliters of fluid infuse each hour. Infusion pumps are programmed in mL/hr, so pump questions ask for it.
The formula: mL/hr = total volume (mL) ÷ total time (hours). If the time is in minutes, divide the minutes by 60 first. For a drug ordered as a dose per hour (units/hr, mg/hr), divide the hourly dose by the bag’s concentration instead.
Pump rates are usually rounded to a whole mL/hr, or to the tenth when the pump allows it. Follow the rounding the question states.
Order: 0.45% sodium chloride 250 mL IV over 4 hours by infusion pump.
- Solve for
- Pump rate (mL/hr)
- Volume
- 250 mL
- Infusion time
- 4 hours
Formula mL/hr = total volume ÷ total hours.
- mL/hr = total volume ÷ total hours.
- 250 mL ÷ 4 hours = 62.5 mL/hr.
- Round to a whole number: 63 mL/hr.
Answer 63 mL/hr
A gravity infusion is counted in drops per minute instead: see gtt.
Sources
- Clinical Calculations: With Applications to General and Specialty Areas — Elsevier (Kee, Marshall, et al.)
- Calculate with Confidence — Elsevier (Morris)