After a prescription has been written it should be carefully reread, the amounts recalculated, and every part carefully reconsidered. It is best to allow some time to elapse between the writing and the rechecking. The best custom is to let all the matter remain in the book when first written and then, if with the patient, give attention to some other matters that will always require attention, then reread carefully each prescription or sheet of instructions as it is torn from the book. This custom possesses the additional advantage that if an error has been made the sheet can be quietly allowed to remain in the book, and a new one written without subjecting the prescriber to the possible embarrassment of acknowledging an error by destroying a prescription in the presence of the patient.