Which abbreviation indicates a dosage measured in 'milligrams'?

The abbreviation that indicates a dosage measured in "milligrams" is "mg." In medical and pharmaceutical contexts, "mg" is the standard abbreviation for milligram, which is a unit of mass equal to one thousandth of a gram. It is commonly used in prescriptions and medication dosages to specify the amount of a drug to be taken.

Understanding this abbreviation is crucial for medication technicians because precise dosing is essential for patient safety and efficacy of treatments. The other options refer to different concepts: "gm" abbreviates grams, which is a larger unit of mass; "sq" is not a standard abbreviation related to dosages but often refers to the term "subcutaneous"; and "po" means "by mouth," indicating the route of administration, not the dosage measurement.