Q.s.

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." However it is written, 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.

Other examples include: 1,q.d.

(qd or QD) is once a day; q.d.

Stands for "quaque die" (which means, in Latin, once a day).

2,b.i.d.

(bid or BID) is twice a day; b.i.d.

Stands for "bis in die" (which means twice a day).

3,t.i.d.

(or tid or TID) is three times a day ; t.i.d.

Stands for "ter in die" (in Latin, 3 times a day).

4,q.i.d.

(or qid or QID) is four times a day; q.i.d.

Stands for "quater in die" (in Latin, 4 times a day).