Browse Medical Abbreviations
O
| O | oxygen [element]; oral; other; ovulation |
| O&E | observation and examination |
| O&G | obstetrics and gynecology |
| O&P | ova and parasites |
| O-A | occipital-atlas |
| o.d. | once daily (L. omni die) |
| O.D. | right eye (L. oculus dexter) |
| o.h. | every hour (L. omni hora) |
| o.m. | every morning (L. omni mane) |
| o.n. | every night (L. omni nocte) |
| O.S. | left eye (L. oculus sinister) |
| O/E | on examination |
| O/R | oral, rectal |
| O2 | oxygen |
| O2Sat | Oxygen saturation (percent) |
| O3 | Omega-3; ozone |
| o: | objective |
| OA | occiput anterior; osteoarthrosis; osteoarthritis |
| OAE | oto acoustic emissions |
| OAG | open-angle glaucoma |
| OAVS | oculoauriculovertebral spectrum |
| OB | obstetrics; occult blood |
| OB+ | occult blood positive |
| OB-Gyn | obstetrics and gynecology |
| OB/GYN | obstetrics/gynecology |
| OBS | organic brain syndrome; obstetrics |
| OBS/OBD | organic brain syndrome/organic brain disorder |
| obsd | observed |
| obst | obstruct, obstruction |
| OBT | over-bed table |
| OBUS | obstetrical ultrasound |
| OC | oral cavity; oleoresin capsicum; obstetrical conjugate; osteocalcin; oral contraceptive |
| occ | occasional |
| OCD | obsessive compulsive disorder |
| OCG | oral cholecystogram |
| OCL | orthopedic cast for limb |
| OCP | oral contraceptive pill |
| OCR | ossicular chain reconstruction |
| OCT | optical coherence tomography; oxytocin challenge test |
| OD | right eye (L. oculus dexter); overdose; Doctor of Optometry; optical density (equivalent to absorbance) |
| ODD | oppositional defiant disorder |
| ODT | orally disintegrating tablet |
| OE | otitis externa |
| OFC | occipital-frontal circumference |
| OFTT | organic failure to thrive |
| OG | orogastric |
| OGD | oesophagogastroduodenoscopy |
| OGT | oral glucose tolerance (test) |
| OGTT | oral glucose tolerance test |
| OH | oral hygiene |
| OH- | hydroxyl ion |
| OHCA | out-of-hospital cardiac arrest |
| OHSS | ovarian hyperstimulation syndrome |
| OI | osteogenesis imperfecta; opportunistic infection |
| OIC | opioid-induced constipation |
| oint | ointment |
| OL | left eye (L. oculus laevus) |
| ol. | oil |
| OLMC | on-line medical control |
| OM | otitis media; osteomalacia |
| OMA | ocular motor apraxia |
| OMB | operational management board |
| OMD | organic mental disorders |
| OME | otitis media with effusion |
| OMFS | oral and maxillofacial surgery |
| OMH | office for migrant health |
| omn. hor. | every hour |
| omn. noct. | every night |
| OmPC | outer membrane protein complex |
| ONH | optic nerve hypoplasia |
| ONJ | osteonecrosis of the jaw |
| ONS | oncology nursing society |
| OoA | Office on Aging |
| OOB | out of bed; out of breath |
| OOH | out of hospital |
| OOR | out of room |
| OOT | out of town |
| OP | occiput posterior; operative; outpatient |
| OPA | outpatient appointment; oropharyngeal airway |
| OPCAB | off-pump coronary artery bypass surgery |
| OPD | outpatient department |
| OPER | outpatient with extended recovery |
| OPG | oculoplethysmography |
| Oph | ophthalmology |
| OPHEP | Office of Public Health Emergency Preparedness (HHS) |
| OPHS | Office of Public Health and Science |
| Ophth | ophthalmology; ophthalmoscope |
| OPMD | oculopharyngeal muscular dystrophy |
| OPMS | oropharyngeal motility study |
| opp | opposite |
| OPQRST | onset, provocation, quality, radiation, severity, time |
| OPROC | outpatient procedure |
| opt | optical; optimal |
| OPT | outpatient |
| OPV | oral polio vaccine |
| OR | odds ratio; operating room |
| ORF | open reading frame |
| org | organization |
| ORIF | open reduction and internal fixation |
| ORL | otorhinolaryngology |
| ORM | operational risk management |
| ORR | objective response rate |
| ORS | oral rehydration solution |
| Orth | orthopedics |
| Ortho | orthopedics |
| Os | osmium [element] |
| OS | left eye (L. oculus sinister) |
| os | mouth; bone |
| OSA | obstructive sleep apnea |
| OSAS | obstructive sleep apnea syndrome |
| OSCE | objective structured clinical examination |
| OSD | over bed side drainage |
| OSHA | Occupational Safety and Health Administration |
| OSHC | Office of Science and Health Coordination |
| OSR | open septo-rhinoplasty |
| osteo | osteo myelitis |
| OT | occupational therapy; occupational therapist |
| OTC | over the counter; ornithine transcarbamylase |
| OTFC | oral transmucosal fentanyl citrate |
| oto | otoscope |
| OTR | registered occupational therapist |
| OTW | over-the-wire |
| OU | both eyes (L. oculi unitas); each eye (L. oculi unitas); Orthodox Union (kosher food indicator) |
| OUD | opioid use disorder |
| OV | office visit |
| OXPHOS | oxidative phosphorylation |
| OXT | oxytocin |
| oz | ounce |
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This content should not be used in place of medically-reviewed decision support reference material or professional medical advice. Abbreviations vary by context and institution. Many abbreviations have alternate or newer meanings not reflected in this set. The abbreviations on this page should not be considered complete.