A nurse is reviewing the medication list of a client. Which of the following medication instructions should the nurse identify as being prescribed using a metric unit?

A) Take 2 drops four times daily: The instruction to take "2 drops" refers to the volume of medication, but drops are typically a non-metric unit of measurement. While some liquid medications are dosed in drops, this is not a metric unit of measurement (such as milliliters or liters). The term "drops" can vary in volume depending on the type of dropper, making it less precise compared to metric units. B) Take 15 mL 1 hr after meals and at bedtime: This instruction uses "mL" (milliliters), which is a metric unit of volume. The metric system includes milliliters as a standard unit for liquid measurement, making this the correct option. This unit is precise and commonly used in clinical settings for administering medications. C) Take 0.5 oz 30 min before meals and at bedtime: "oz" stands for ounces, which is an imperial unit of measurement, not a metric unit. While ounces are commonly used, they are not part of the metric system. The metric equivalent of ounces is milliliters (mL), but "oz" itself is not a metric unit. D) Take 1 tsp four times daily: "tsp" stands for teaspoon, which is a unit of volume in both the imperial and metric systems. However, teaspoons are not strictly a metric unit when compared to milliliters (mL) or liters (L), even though a teaspoon is sometimes defined as 5 mL in the metric system. It is a more informal or hybrid measurement, and while it is used in both systems, it is not a pure metric unit like milliliters.