Q:

# How Do You Calculate Medication Dosage?

A:

Medication dosage is calculated using a standard equation, designed to prevent a medication error that could affect patient outcomes, according to Nursing Times. The equation calls for dividing “what you want” by “what you have” and multiplying by “what it’s in,” which can be modified to suit a particular clinical situation.

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There are three basic types of medication dosage calculations, which include a volume to be administered, infusion rates, and weight-based dosages, are all calculated given a concentration on hand. Weights, volumes and times must use the same units of measurement in each calculation to ensure accurate results. To calculate the volume to administer, the desired dose is divided by the dose of the provided medication and then multiplied by the volume in which the medication is contained.

To calculate an infusion rate, calculate the volume to be administered. Divide that by the time that the infusion is to run over. If the desired medication dosage is per hour, then the infusion pump is set to the calculated volume to be administered. If the medication dosage is supposed to run over four hours, for example, then divide the volume to be administered by 4 to calculate the infusion rate per hour.

To calculate a weight-based dose, convert the patient’s weight into kilograms by dividing the provided weight by 2.2, because there are 2.2 pounds in every kilogram. Calculate the weight-based desired dose by multiplying the desired dose by the weight. Follow the same steps as explained above to calculate the volume to be administered, and the infusion rate if needed.