There are three common measurement systems used in health care--metric, household, and apothecary systems. Nurses must be able to convert each of these systems to the other for proper medication administration through several methods. Desired dosage is a prescribed dose, and is calculated according to the available dose, volume and quantity.
Oral dosages can be administered in solid or liquid and are typically calculated in milligrams or milliliters.
Injectable dosages are commonly administered through a syringe in fluid or liquid, and are also typically calculated in milligrams or milliliters.
Intravenous dosages are administered electronically or manually in patients. These require calculating flow rates, duration, drip rates, and volume of dosage.
Topical medications are administered on patients, and dosages are calculated for the height and weight of a patient.
All medical dosages require several different mathematical calculations and can include using basic math, fractions, ratios and several different measurement systems. These calculations are used by nurses on a daily basis.