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Medical Abbreviations – O



O objective
OA Osteoarthritis
obstructive apnea
occipital artery
on admission
on arrival
old age
O&A observation and assessment
OAA Old Age Assistance
OAB overactive bladder
old age benefits
OAC oral anticoagulant
omeprazole, amoxicillin and clarithromycin
oral activated charcoal
OAD obstructive airway disease
occlusive arterial disease
obliterative airway disease
other articular diseases
obscure auditory dysfunction
OAE otoacoustic emissions
OAF osteoclast activating factor
open air factor
oroantral fistula
OAG open angle glaucoma
Oral Assessment Guide
OAM omeprazole, amoxicillin, and metronidazole
Office of Alternative Medicine
OAP Ophthalmic Artery Pressure
over-anxious patient
OARS organs at risk
OAS Office of Applied Studies
oral allergy syndrome
oral anticoagulants
organic anxiety syndrome
Oral appliances
overall survival
Ostomy Adjustment Scale
OAT oral anticoagulant therapy
Optometry Admission Test
open artery trial
OAV oculo-auriculo-vertebral
ovine adenovirus
OB obstetrics
occult blood
occlusion body
olfactory bulb
OBA office-based anesthesia
OBD obscure digestive bleeding
organic brain disease
Opioid bowel dysfunction
OBE out-of-body experience
OBF ocular blood flow
organ blood flow
ovarian blood flow
OBG obstetrics and gynecology
OBJ objective
OBL oblique
OBP odorant-binding protein
office blood pressure
ova, blood, parasites
OBR obesity gene receptor
ortho bowel routine
OB receptor
OBS observation
organic brain syndrome
occlusion bodies
OBT obtained
OBW obese black women
open bed warmer
OC oral contraceptive
office call
on call
oral cavity
oral care
only child
observed cases
O&C onset and course
OCA open care area
ovarian carcinoma
Obsessive Compulsive Anonymous
oral contraceptive agent
Operative Care Advised
OCB obstructive chronic bronchitis
obsessive-compulsive behavior
OCC occasional
OCCL occlusion
OCCM open chest cardiac massage
OCD obsessive-compulsive disorder
organ-confined disease
OCE outpatient code editor
oral conjugated estrogens
observable cholinomimetic effects
OCG oral cholecystogram
OCI Obsessive-Compulsive Inventory
obliquus capitis inferior (neck muscle)
OCL oral colonic lavage
OCN oculomotor nucleus
obsessive-compulsive neurosis
Oncology Certified Nurse
OCP oral contraceptive pill
oral case presentation
OCR oculocephalic reflex
oxygen consumption rate
oculocardiac reflex
outpatient cardiac rehabilitation
OCS oral contraceptives
open canalicular system
Obsessive-Compulsive Scale
obsessive-compulsive symptoms
obstetric complications
OCT optical coherence tomography
Oral contraceptive therapy
oxytocin challenge test
oral cavity tumor
OCU observation care unit
OCVM occult cerebrovascular malformations
OCX oral cancer examination
occipital cortex
OD overdose
right eye
Doctor of Optometry
once daily
ocular dominance
on duty
optic disc
occupational disease
ODA on day of admission
Operating Department Assistant
Orphan Drug Act
ODC oxygen dissociation curve
oxyhemoglobin dissociation
outpatient diagnostic center
ODD Oppositional-Defiant Disorder
Once-daily dosing
ODE optic disc edema
outer dental epithelium
ODI Oswestry Disability Index
oxygen desaturation index
ODM occlusion dose monitor
ODN open donor nephrectomy
optokinetic nystagmus
ODP Ocular dominance plasticity
occipitodextra posterior
offspring of diabetic parents
ODQ on direct questioning
Oswestry Disability Questionnaire
ODS Office of Dietary Supplements
osmotic demyelination syndrome
Office of Drug Safety
Oswestry Disability Score
ODT orally disintegrating tablet
optical Doppler tomography
occipitodextra transerve
OE on examination
otitis externa
open eyes
orthopedic examination
OEC oxygen equilibrium curve
olfactory ensheathing cell
outer ear canal
OEI opioid escalation index
Obesity Education Initiative
Office of Evaluation and Inspections
OEL occupational exposure level/limits
OENT oral endotracheal tube
OEP olfactory evoked potentials
operational effectiveness program
Office of Emergency Preparedness
OER oxygen extraction ratio
oxygen enhancement ratios
oestrogen receptor
OET oral esophageal tube
open epicutaneous test
oral endotracheal tube
OF opacity factor
open field
organ failure 
optic fundi
osteitis fibrosa
osteitis fibrosa
OFC occipitofrontal circumference
oral food challenge
osteitis fibrosa cystica
orofacial clefts
OFG orofacial granulomatosis
OFI other febrile illness
ocular fixation index
OFLOX ofloxacin
OFM open-face mask
oral focal mucinosis
OFR oxygen-free radicals
ocular following response(s)
OFS osteoplastic frontal sinusotomy
occasions for smoking scale
organ failure score
OFTT organic failure to thrive
oral fat tolerance test
OG Obstetrics & Gynecology
oral glucose
osmolality gap
OGC oculogyric crisis
oral glutamine challenge
OGCT oral glucose challenge test
ovarian germ cell tumor
OGD oesophagogastroduodenoscopy
oxygen and glucose deprivation
OGIB obscure gastrointestinal bleeding
OGNP Obstetric-Gynecology Nurse Practitioner
OGT orogastric tube
oral glucose tolerance
OH occupational health
occupational history
obstetric history
ocular history
orthostatic hypotension
ocular hypertension
oral hypoglycemic
oral hygiene
OHA oral hypoglycemic agents
OHC outer hair cell
OHD organic heart disease
OHF old healed fracture
omsk hemorrhagic fever
OHG oral hypoglycemic
optico-hypothalamic gliomas
OHI oral hygiene instructions /index
OHL oral hairy leukoplakia
occupational hearing loss
OHP oxygen at high pressure
obese hypertensive patient
OHS obesity hypoventilation syndrome
occupational health service(s)
Oslo Hypertension Study
open heart surgery
OHT ocular hypertension
orthotopic heart transplantation
orthostatic hypertension
OI opportunistic infection
oxygen index
osteogenesis imperfecta
otitis interna
obesity index
OIC opioid-induced constipation
osteogenesis imperfecta congenita
OIF oil-immersion field
observed intrinsic frequency
OIG Office of the Inspector General
OIH orthoiodohippurate
ovulation-inducing hormone
OIM Obturator internus muscle
optical immunoassay
OINT ointment
OIR oxygen-induced retinopathy
OIS ocular ischemic syndrome
opportunistic infections
Office of Information Systems
Organ Injury Scaling
OIT ovarian immature teratoma (rare ovarian cancer)
oral immunotherapy
OJ orange juice
obstructive jaundice
OK obstructed kidney
all right
OKAN optokinetic after nystagmus
OKC odontogenic keratocyst
OKN optokinetic nystagmus
OL olfactory lobe
orbital layer
open label
optic lobes
OLB open-liver biopsy
open-lung biopsy
olfactory bulb
OLC ouabain-like compound
osteoclast-like cell
OLD obstructive lung disease
OLE occipital lobe epilepsy
OLF olfactory
ouabain-like factor(s)
OLM ocular larva migrans
OLP oral lichen planus
OLR oral lichenoid reactions
OLS ouabain-like substance
operating limits
OLT orthotopic liver transplant
OLV one-lung ventilation
OLZ olanzapine
OM otitis media
ovulation method
outer membrane
obtuse marginal
ocular movement
oral motor
OMA ocular motor apraxia
older maternal age
OMAC otitis media, acute, catarrhal
OMAS Oral Mucositis Assessment Scale
otitis media, acute, suppurating
OMB obtuse marginal branch
OMC open mitral commissuortomy
oculomotor complex
OMD organic mental disorder
ocular muscle dystrophy
OME otitis media with effusion
oral morphine equivalent
Office of Medical Examiner
OMG ocular myasthenia gravis
OMI old myocardial infarction
Oral Mucositis Index
OMP outer membrane protein
oculomotor palsy
OMR Online Medical Record
operative mortality rate
oculomotor range
OMS organic mental syndrome
opsoclonus-myoclonus syndrome
oral morphine sulfate
OMT oral mucosal transudate
osteopathic manipulative treatment
OMVC open mitral valve commissurotomy
OMVD optimized microvessel density
ON optic nerve
optic neuritis
over night
ONB olfactory neuroblastoma
ONC Oncology
over-the-needle catheter
Orthopedic Nurse, Certified
OND ondansetron
other neurological disorders
optic nerve disease
ONH optic nerve head
optic nerve hypoplasia
ONJ osteonecrosis of the jaw
ONM ocular neuromyotonia
ONSD optic nerve sheath decompression
ONSF optic nerve sheath fenestration
ONTD open neural tube defect(s)
ONTR orders not to resuscitate
OO oophorectomy
ophthalmic ointment
oral order
orbicularis oculi
OOB out of bed
OOC odontogenic cyst
onset of contractions
out of cast
Outlet obstructive constipation
OOH out of hospital
OOL onset of labor
OOM onset of menarche
oogonial metaphase
OOP out of pocket
out of pelvis
OOR orbicularis oculi reflex
out of room
OOS orbicularis oris superior
out of sequence
OOW out of wedlock
out of work
OP osmotic pressure
opening pressure
obese patient
O&P ova and parasites
OPA oropharyngeal airway
OPAT outpatient parenteral antibiotic therapy
OPB outpatient basis
open brain
OPC Objective Performance Criteria
outpatient care
Office of Primary Care
oropharyngeal candidiasis
OPD outpatient department
obstructive pulmonary disease
oropharyngeal dysphagia
oculopharyngeal dystrophy
OPE outpatient evaluation
OPG ocular plethysmography
oocysts per gram
OPK ovulation predictor kit
OPL other party liability
oral premalignant lesion
OPM occult primary malignancy
OPN operation
open partial nephrectomy
OPO organ procurement organizations
OPP oppose
Organophosphate poisoning
OPS Objective Pain Scale
optical position sensor
OPT Ovulation Predictor Test
OPV oral polio vaccine
outpatient visit
OR operating room
odds ratio
open reduction
ORD optical rotatory dispersion
ORL Otorhinolaryngology
oblique retinacular ligament
ORN operating room nurse
OROS oral osmotic
ORP operating room personnel
oxidation-reduction potentials
occiput right posterior
ORR overall response rate
objective response rate
ORS olfactory reference syndrome
oral rehydration solution
oculo-respiratory syndrome
ORT operating room technician
oral rehydration therapy
OS left eye
overall survival
open surgery
oral surgery
occupational safety
OSA obstructive sleep apnea
OSC open sigmoid colectomy
oral self-care
OSD Osgood-Schlatter disease
occupational skin disease
OSE ovarian surface epithelium
OSM osmolarity
OSN olfactory sensory neuron
off-service note
OSP Oligodendrocyte-specific protein
Oral Sodium Phosphate
OSR open surgical repair
overall survival rate
OSS osseous
OST out-of-school-time
Ottawa Stroke Trial
overall survival time
OT objective test
Occupational Therapist
occupational therapy
occlusion time
office therapy
OTA occupational therapy assistant
open to air
OTC over-the-counter
off the case
OTD optimal therapeutic dose
oral temperature device
OTE optically transparent electrode
Overall Treatment Evaluation
OTO otology
one-time only
OT/RT occupational therapy/recreational therapy
OTS optical tracking system
orotracheal suction
oxygen transport system
OTT oral transit time
overall treatment time
oesophageal transit time
OTW over the wire
OU both eyes / each eye
OUES oxygen uptake efficiency slope
OULQ outer upper left quadrant
OURQ outer upper right quadrant
OUS obstetric ultrasound
observation units
OV office visit
osteoid volume
OVCA ovarian cancer
OVD occlusal vertical dimension
ophthalmic viscoelastic device
OVLT organum vasculosum of lamina terminalis
OVR Office of Vocational Rehabilitation
oculovestibular reflex
OVS overall survival
obstructive voiding symptoms
OW once weekly
open wound
oval window
OX oxalate
OXA oxacillin
OXC oxcarbazepine
OXT oxytocin
OZ ounce
optical zone
Medical Abbreviations – O