O

O2 – oxygen

O2 sat – oxygen saturation

OA – osteoarthritis

OB – obstetrics

OBB – out of bed

Obesity – excess body fat

Obstipation – constipation

Obs – observation

OCD – obsessive compulsive disorder

OD – right eye, once daily

O/E – on examination

OG – orogastric

OGTT – oral glucose tolerance test

OM – otitis media

OOB – out of bed

OPA – oropharyngeal airway

OPAT – outpatient parenteral antimicrobial therapy

OPD – outpatient department

OPIM – other potentially infectious materials

OPV – oral polio vaccine

OR – operating room

OREF – open reduction and external fixation

ORIF – open reduction and internal fixation

Ortho – orthostatic

OS – left eye

OSA – obstructive sleep apnea

OSH – outside hospital

OSHA – occupational safety and health

Osteoporosis – weak bones

OT – occupational therapy, operating theatre

OTC – over the counter

OU – both eyes

OUD – opioid use disorder

Outpt – outpatient

OX – oximetry

OZ – ounce