Ophth
opthalmic
OTC
Over the counter
OJ
Orange Juice
OD
overdose
OC
Oral contraceptive
ODC
Oral Disintegrating tablet
OM
Otis media
O:
objective
o.s.;OS
left eye
oz
ounce
oint.
ointment
OTC
Over the counter
o.u.;OU
both eyes, each eye
o.d.;OD
Right eye
O2
oxygen