Serious medication errors, including patient deaths, have occurred because oral liquids are prescribed and/or administered using English measurement units such as the teaspoon or tablespoon. For medical professionals, best practice is using units and volume when prescribing a single-agent liquid medication, to be sure the dose is clear; but for administering, use only mL for measuring the amount. Safety organizations and agencies such as the CDC and the Institute for Safe Medication Practices have recommended using only the metric system units (e.g., mL) for measurement and using a measuring device that contains only metric markings. Prescribing using the metric system and dispensing with a metric measuring device will help avoid these preventable errors.