On which day of the month does a drug typically expire?

Many medications typically have expiration dates set at the end of a month rather than on specific days like the 1st, 15th, or 30th. Setting the expiration on the last day of the month provides a clear-cut reference point for when the drug is no longer guaranteed to be safe or effective. This practice simplifies inventory management and ensures that both pharmacy staff and consumers have a consistent understanding of drug stability. Expiration dates are determined based on stability studies conducted by manufacturers, and these studies often lead to a standard practice of marking the end of a month as the expiration date for the sake of clarity and precaution. This is why the last day of the month is the correct choice for when a drug typically expires.