List of medical abbreviations: Latin abbreviations

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 there.

Abbrev.	Meaning	Latin (or New Latin) origin	Avoid abbreviating[1][2]
a.c.	before meals	ante cibum
a.d., ad, AD	right ear	auris dextra	spell out[1]
a.m., am, AM	morning	ante meridiem
a.s., as, AS	left ear	auris sinistra	spell out[1]
a.u., au, AU	both ears together or each ear	aures unitas or auris uterque	spell out[1]
b.d.s, bds, BDS	2 times a day	bis die sumendum
b.i.d., bid, bd	twice a day / twice daily / 2 times daily	bis in die	spell out[2]
gtt., gtt	drop(s)	gutta(e)
h., h	hour	hora
h.s., hs	at bedtime or half strength	hora somni	spell out[1]
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	spell out[2]
o.d., od, OD	once a day right eye	omne in die oculus dexter	spell out[1][2]
o.s., os, OS	left eye	oculus sinister	spell out[1]
o.u., ou, OU	both eyes	oculus uterque	spell out[1]
p.c.	after food	post cibum
p.m., pm, PM	afternoon or evening	post meridiem
p.o., po, PO	orally / by mouth / oral administration	per os / nonstandard form per orem	spell out "orally"[1][2]
p.r., pr, PR	rectally	per rectum
p.r.n., prn, PRN	as needed, (also Pertactin - a key antigen of ac.Pertussis vaccine)	pro re nata	spell out[2]
q.	every	quaque
q.1.d., q1d	every day	quaque die	spell out[1]
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	spell out[1][2]
q.h.s., qhs	every night at bedtime	quaque hora somni	spell out[1]
q.d.s, qds, QDS	4 times a day	quater die sumendum
q.i.d, qid	4 times a day	quater in die	spell out[2]
q.h., qh	every hour, hourly	quaque hora
q.o.d., qod	every other day / alternate days	quaque otra die	spell out[1][2]
q.p.m., qPM, qpm	every afternoon or evening	quaque post meridiem
q.s., qs	a sufficient quantity (enough)	quantum sufficiat
Rx, Rx, , ℞	prescription	recipe
Sig., S.	directions	signa
Stat.	immediately, with no delay, now	statim
t.d.s, tds, TDS	3 times a day	ter die sumendum
t.i.d., tid	3 times a day	ter in die	spell out[2]
u.d., ud	as directed	ut dictum	spell out[1]

References

1. Institute for Safe Medication Practices, ISMP’s List of Error-Prone Abbreviations, Symbols, and Dose Designations (PDF).
2. American Medical Association, "Section 14.11", AMA Manual of Style.