Obesity
Obsessive-Compulsive Disorder
Occupational Health
Occupational Injuries see Occupational Health
Occupational Therapy see Rehabilitation

Ombudsman Programs see Patient Issues
Oncology see Cancer (General)
Ophthalmology see Eye Diseases (General)
Opiates see Drug Abuse ; Heroin Abuse
Optic Neuritis
Oral Cancer
Oral Lichen Planus

Oral Tobacco see Smokeless Tobacco
Orchitis
Organ Donation
Organ Transplantation
Osteoarthritis
Osteochondritis Dissecans
Osteogenesis Imperfecta

Osteomalacia
Osteomyelitis see Bone Diseases
Osteonecrosis
Osteoporosis
Osteosarcoma see Bone Cancer
Ostomy

Otitis Media see Ear Infections
Ovarian Cancer
Ovarian Cysts
Overactive Bladder see Urinary Incontinence
Overweight see also Obesity

Oxygen Therapy
Ozone