| Abbreviations | Meaning |
 | ODHA | Oregon Dental Hygienists Association |
 | ODPHP | Office Of Disease Prevention And Health Promotion |
 | ODQ | Ordre Des Dentistes Du Québec |
 | ODS | Office Of Dietary Supplements |
 | ODST | Online Depression Screening Test |
 | OEB / EPO / EPA | Office Européen Des Brevets / European Patent Office / Europäisches Patentamt |
 | OECD / OCDE | Organisation For Economic Co-operation And Development / Organisation De Coopération Et De Développement Economiques |
 | OECI | Organisation Of European Cancer Institutes |
 | OEDT / EMCDDA | Observatoire Européen Des Drogues Et Des Toxicomanies / European Monitoring Centre For Drugs And Drug Addiction |
 | OEGGG | Österreichischen Gesellschaft Für Gynäkologie Und Geburtshilfe |
 | OEHHA | Office Of Environmental Health Hazard Assessment |
 | OEI | Obesity Education Initiative. National Heart, Lung, And Blood Institute. |
 | OEM | Occupational And Environmental Medicine [periodical] |
 | OER | NIH Office Of Extramural Research |
 | OERTC | Organisation Européenne De Recherche Sur Le Traitement Du Cancer |
 | OESO | World Organization For Specialized Studies On Diseases Of The Esophagus |
 | OFA | Orthopedic Foundation For Animals |
 | OFDT | Observatoire Français Des Drogues Et Des Toxicomanies. French Monitoring Centre For Drugs And Drug Addiction |
 | OFEDO | Organización De Facultades, Escuelas Y Departamentos De Odontología. Organization Of Faculties, Schools, And Departments Of Dentistry |
 | OFP | Office Of Family Planning |
 | OFRC | Oklahoma Family Resource Coalition |
 | OFSP / BAG / FOPH / UFSP | Office Fédéral De La Santé Publique / Bundesamt Für Gesundheit / Federal Office Of Public Health / Ufficio Federale Della Sanità Pubblica |
 | ÖGARI | Österreichische Gesellschaft Für Anaesthesiologie, Reanimation Und Intensivmedizin |
 | ÖGDV | Österreichische Gesellschaft Für Dermatologie Und Venerologie. Austrian Society Of Dermatology And Venereology |
 | ÖGES | Österreichische Gesellschaft Für Endokrinologie Und Stoffwechsel. Austrian Society Of Endocrinology And Metabolism |
 | ÖGIAIM | Österreichische Gesellschaft Für Internistische Und Allgemeine Intensivmedizin |
 | OH | Osteopathic Hospitals [periodical] |
 | OHA | Ontario Homeopathic Association |
 | OHA | Ontario Hospital Association |
 | OHA | Oral Health America |
 | OHAP | Office Of HIV/AIDS Policy |
 | OHASA | Oral Hygienists Association Of South Africa |
 | OHCEN | Ontario Health Care Evaluation Network |
 | OHDQ | Ordre Des Hygiénistes Dentaires Du Québec |
 | OHE | Office Of Health Economics |
 | OHF | Oxalosis And Hyperoxaluria Foundation |
 | OHIMA | Ohio Health Information Management Association |
 | OHLA | Ontario Health Libraries Association |
 | OHPCO | Ohio Hospice & Palliative Care Organization |
 | OHRE | Office Of Human Radiation Experiments. Department Of Energy |
 | OHRP | Office Of Human Research Protection |
 | OHSLA | Ohio Health Sciences Library Association |
 | OHSR | Office Of Human Subjects Research |
 | OI FOUNDATION | Osteogenesis Imperfecta Foundation |
 | OIA | Ophthalmic Imaging Association |
 | OICS / INCB / JIFE | Organe International De Contrôle Des Stupéfiants / International Narcotics Control Board / Junta Internacional De Fiscalización De Estupefacientes |
 | OIE | Office International Des Épizooties. Organisation Mondiale De La Santé Animale. World Organisation For Animal Health. Organización Mundial De Sanidad Animal. |
 | OIFE | Osteogenesis Imperfecta Federation Europe |
 | OIIO / CNO | Ordre Des Infirmières Et Infirmiers De L'Ontario / College Of Nurses Of Ontario |
 | OIIQ | Ordre Des Infirmières Et Infirmiers Du Québec |