| OMH | Office of Mental Health |
|---|---|
| OMI | office of medical investigator; old myocardial infarction |
| ON | occipitonuchal; office nurse; onlay; optic nerve; orthopedic nurse; osteonecrosis; osteonectin; over... |
| OPHC | Office of Prepaid Health Care |
| OPRR | Office of Protection from Research Risks |