q_h (on prescription)

If a medicine is to be taken every so- many hours, it is written "q_h"; the "q" standing for the Latin word for once "quaque" and the "h" indicating the number of hours. So, for example, "2 caps q4h" means "Take 2 capsules every 4 hours." It is one of a number of hallowed abbreviations of Latin terms that have been traditionally used in prescriptions to specify the frequency with which medicines should be taken.