A collection of organizations providing health information arranged by topic. Also available in alphabetical order.
Obesity
- American Society of Bariatric Physicians
- National Heart, Lung, and Blood Institute
- National Institute of Diabetes and Digestive and Kidney Diseases
- Weight-Control Information Network (National Institute of Diabetes and Digestive and Kidney Diseases)
Obesity in Children
- KidsHealth (Nemours Foundation)
- National Institute of Diabetes and Digestive and Kidney Diseases
- Weight-Control Information Network (National Institute of Diabetes and Digestive and Kidney Diseases)
Obsessive-Compulsive Disorder
- American Psychiatric Association
- Anxiety and Depression Association of America
- International OCD Foundation
- National Institute of Mental Health
Occupational Health
- American College of Medical Toxicology
- Department of Labor
- Job Accommodation Network (Office of Disability Employment Policy)
- National Institute for Occupational Safety and Health
- National Toxicology Program
- Occupational Safety and Health Administration
Occupational Health for Health Care Providers
- American Association of Occupational Health Nurses
- Centers for Disease Control and Prevention
- Department of Labor
- National Institute for Occupational Safety and Health
- Occupational Safety and Health Administration
Oil Spills
Opioid Abuse and Addiction
- Centers for Disease Control and Prevention
- Drug Enforcement Administration
- Food and Drug Administration
- National Institute on Drug Abuse
- Partnership at Drugfree.org (Partnership for a Drug-Free America)
- Substance Abuse and Mental Health Services Administration
Oral Cancer
- American Academy of Otolaryngology--Head and Neck Surgery
- American Association of Oral and Maxillofacial Surgeons
- American Cancer Society
- American Head and Neck Society
- National Cancer Institute
- National Institute of Dental and Craniofacial Research
- Oral Cancer Foundation
Organ Donation
- American Association of Tissue Banks
- Donate Life America
- Eye Bank Association of America
- National Organ and Tissue Donation Initiative (Health Resources and Services Administration)
- United Network for Organ Sharing
Organ Transplantation
- American Society of Transplantation
- National Institute of Allergy and Infectious Diseases
- Organ Procurement and Transplantation Network
- United Network for Organ Sharing
Orthodontia
- American Association of Orthodontists
- American Dental Association
- National Institute of Dental and Craniofacial Research
Osteoarthritis
- American College of Rheumatology
- Arthritis Foundation
- National Institute of Arthritis and Musculoskeletal and Skin Diseases
Osteogenesis Imperfecta
- National Institute of Arthritis and Musculoskeletal and Skin Diseases
- National Institutes of Health Osteoporosis and Related Bone Diseases~National Resource Center (National Institute of Arthritis and Musculoskeletal and Skin Diseases)
- Osteogenesis Imperfecta Foundation
Osteonecrosis
- American Academy of Orthopaedic Surgeons
- National Institute of Arthritis and Musculoskeletal and Skin Diseases
- National Osteonecrosis Foundation
Osteoporosis
- International Osteoporosis Foundation
- National Institute of Arthritis and Musculoskeletal and Skin Diseases
- National Institutes of Health Osteoporosis and Related Bone Diseases~National Resource Center (National Institute of Arthritis and Musculoskeletal and Skin Diseases)
- National Osteoporosis Foundation
Ostomy
- American Society of Colon and Rectal Surgeons
- National Institute of Diabetes and Digestive and Kidney Diseases
Ovarian Cancer
- American Cancer Society
- National Cancer Institute
- National Ovarian Cancer Coalition
- womenshealth.gov (Department of Health and Human Services, Office on Women's Health)
Ovarian Cysts
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (National Institute of Child Health and Human Development)
- womenshealth.gov (Department of Health and Human Services, Office on Women's Health)
Ovarian Disorders
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (National Institute of Child Health and Human Development)
- womenshealth.gov (Department of Health and Human Services, Office on Women's Health)
Over-the-Counter Medicines
Overactive Bladder
- National Association for Continence
- National Institute of Diabetes and Digestive and Kidney Diseases
Oxygen Therapy
- American College of Chest Physicians
- American Lung Association
- National Heart, Lung, and Blood Institute