Please enter valid positive numbers for all fields.
Set IV Pump To:
0
mL/hr
Concentration: 0 g/mL
Medical Disclaimer: This tool is for educational purposes only and does not replace professional clinical judgment. Always double-check calculations and follow your facility's protocols before administering medication. Magnesium Sulfate is a high-alert medication.
function calculateMagDrip() {
// Get DOM elements
var magInput = document.getElementById('totalMagGrams');
var volInput = document.getElementById('totalVolumeMl');
var doseInput = document.getElementById('orderedDose');
var resultBox = document.getElementById('resultBox');
var resultDisplay = document.getElementById('flowRateResult');
var concDisplay = document.getElementById('concentrationResult');
var errorMsg = document.getElementById('calcError');
// Parse values
var totalMag = parseFloat(magInput.value);
var totalVol = parseFloat(volInput.value);
var orderedDose = parseFloat(doseInput.value);
// Reset UI
resultBox.style.display = 'none';
errorMsg.style.display = 'none';
// Validation
if (isNaN(totalMag) || totalMag <= 0 ||
isNaN(totalVol) || totalVol <= 0 ||
isNaN(orderedDose) || orderedDose < 0) {
errorMsg.style.display = 'block';
return;
}
// Calculation Logic
// Formula: (Ordered Dose (g/hr) * Total Volume (mL)) / Total Drug (g) = Rate (mL/hr)
var concentration = totalMag / totalVol; // g/mL
var flowRate = orderedDose / concentration; // (g/hr) / (g/mL) = mL/hr
// Display Results
// IV pumps usually allow 1 decimal place, sometimes integers depending on model.
// We will show 1 decimal place for precision.
resultDisplay.innerHTML = flowRate.toFixed(1);
concDisplay.innerHTML = concentration.toFixed(4); // Display concentration for verification
resultBox.style.display = 'block';
}
Guide to Calculating Magnesium Sulfate Drip Rates
Magnesium Sulfate is a high-alert medication frequently used in obstetrics for the prevention of seizures in preeclampsia/eclampsia and for neuroprotection in preterm fetuses. It is also used in other medical settings for severe asthma or hypomagnesemia. Accurate calculation of the IV drip rate is critical for patient safety.
The Formula
To calculate the flow rate in milliliters per hour (mL/hr) based on an ordered dose in grams per hour (g/hr), use the following formula:
Rate (mL/hr) = [Ordered Dose (g/hr) × Total Volume (mL)] ÷ Total Amount of Drug (g)
Alternatively, you can determine the concentration first:
Calculate Concentration: Total Grams ÷ Total Volume = Grams per mL.
Most hospitals utilize standard premixed bags to reduce calculation errors. Below are the most common concentrations found in clinical settings:
Total Mag (g)
Total Volume (mL)
Concentration
Rate for 2g/hr Dose
40 g
1000 mL
0.04 g/mL
50 mL/hr
20 g
500 mL
0.04 g/mL
50 mL/hr
20 g
1000 mL
0.02 g/mL
100 mL/hr
Clinical Considerations
Loading Dose: Magnesium sulfate therapy often begins with a "loading dose" (e.g., 4-6 grams over 20-30 minutes) before switching to the maintenance rate calculated above.
Maintenance Dose: The typical maintenance infusion rate ranges from 1g/hr to 3g/hr depending on patient renal function and serum magnesium levels.
Monitoring: Patients on a magnesium drip require frequent monitoring of deep tendon reflexes, respiratory rate, and urine output to detect signs of toxicity.
Double Check: Because this is a high-alert medication, calculations and pump settings should always be independently verified by a second registered nurse.
Frequently Asked Questions
What is the standard concentration of Mag Sulfate?
While it varies by facility, a very common standard concentration is 40 grams in 1000 mL of Sterile Water or Lactated Ringer's, resulting in a concentration of 0.04 g/mL (1 gram = 25 mL).
How do I convert g/hr to mL/hr?
You must know the concentration of your solution. Divide your ordered dose (g/hr) by the concentration of the bag (g/mL) to get the pump setting in mL/hr.
What if the patient has renal impairment?
Magnesium is excreted by the kidneys. In patients with renal impairment (low urine output or high creatinine), the maintenance dose is often reduced (e.g., to 1g/hr) to prevent toxicity.