Which abbreviation means 'As needed'?

The abbreviation that means 'as needed' is "prn," which stands for the Latin phrase "pro re nata." This is commonly used in medical contexts to indicate that a medication or treatment should be administered only when required, rather than at scheduled intervals. For example, a physician may instruct a patient to take pain medication prn, meaning they should take it only if they are experiencing pain, rather than on a regular schedule.

Understanding this abbreviation is critical for medical assistants, as it helps ensure patient care is tailored to individual needs, avoiding unnecessary medication use. Other options represent different medical terms: "QID" refers to taking medication four times a day, "AC" means before meals, and "mcg" is a measurement unit for micrograms. Recognizing these distinctions is vital for proper documentation and patient communication in a clinical environment.