Which assessment is crucial for a nurse to perform prior to administering a new medication?

The assessment of allergies and past reactions is critical prior to administering a new medication because it directly relates to the patient's safety. Knowing a patient's allergies helps the nurse identify any potential adverse reactions to the medication, which could be life-threatening in some cases. A history of allergic reactions can guide the healthcare provider in avoiding medications that could pose risks to the patient’s health, thus preventing complications and ensuring the medication prescribed will be safe for them.

While the other assessments listed may be important in different contexts, they do not hold the same immediate relevance to the safe administration of a medication. Family medical history can provide insights into the patient’s risk factors for certain conditions, but it doesn't specifically address immediate medication safety as allergies do. Financial situations may impact a patient's ability to afford medications but do not impact the pharmacological safety of the medication itself. Assessing literacy levels can facilitate effective communication and understanding of medication instructions, yet it does not influence the actual administration safety directly, making the assessment of allergies the most crucial step.