The main discussion of these abbreviations in the context of drug prescriptions and other medical prescriptions is at List of abbreviations used in medical prescriptions. Some of these abbreviations are best not used, as marked and explained here.
| Abbrev. | Meaning | Latin (or Neo-Latin) origin |
|---|---|---|
| a.c. | before meals | ante cibum |
| a.d., ad, AD | right ear | auris dextra |
| a.m., am, AM | morning | ante meridiem |
| nocte | every night | Omne Nocte |
| a.s., as, AS | left ear | auris sinistra |
| a.u., au, AU | both ears together or each ear | aures unitas or auris uterque |
| b.d.s, bds, BDS | 2 times a day | bis die sumendum |
| b.i.d., bid, BID | twice a day / twice daily | bis in die |
| gtt., gtts | drop(s) | gutta(e) |
| h., h | hour | hora |
| qhs, h.s., hs | at bedtime or half strength | quaque hora somni |
| ii | two tablets | duos doses |
| iii | three tablets | trēs doses |
| n.p.o., npo, NPO | nothing by mouth / not by oral administration | nil per os |
| o.d., od, OD | right eye
once a day (United Kingdom) |
oculus dexter
omne in die |
| o.s., os, OS | left eye | oculus sinister |
| o.u., ou, OU | both eyes | oculus uterque |
| p.c. | after food | post cibum |
| p.m., pm, PM | afternoon or evening | post meridiem |
| p.o., po, PO | by mouth / oral administration | per os / nonstandard form per orem |
| p.r., pr, PR | rectally / rectal administration | per rectum |
| p.r.n., prn, PRN | as needed | pro re nata |
| q. | every | quaque |
| q.1.h., q1h | every hour | quaque hora |
| q.2.h., q2h | every 2 hours | quaque secunda hora |
| q.4.h., q4h | every 4 hours | quaque quarta hora |
| q.6.h., q6h | every 6 hours | quaque sexta hora |
| q.8.h., q8h | every 8 hours | quaque octava hora |
| q.a.m., qAM, qam | every morning | quaque ante meridiem |
| q.d., qd | every day / daily | quaque die |
| q.h.s., qhs | every night at bedtime | quaque hora somni |
| q.d.s, qds, QDS | 4 times a day | quater die sumendum |
| q.i.d, qid | 4 times a day | quater in die |
| q.h., qh | every hour, hourly | quaque hora |
| q.o.d., qod | every other day / alternate days | quaque altera die |
| q.p.m., qPM, qpm | every afternoon or evening | quaque post meridiem |
| q.s., qs | a sufficient quantity (enough) | quantum sufficiat |
| q.wk. also qw | weekly (once a week) | quaque week |
| Rx, Rx, ℞ | prescription | recipe |
| Sig., S. | directions | signa |
| Stat. | immediately, with no delay, now | statim |
| t.i.d., tid, TID | 3 times a day | ter in die |
| t.d.s., tds, TDS | take by mouth 3 times a day | ter die sumendus |
| u.d., ud | as directed | ut dictum |
.