Insurance against loss by illness or bodily injury. Health insurance provides coverage for medicine, visits to the doctor or emergency room, hospital stays and other medical expenses. Policies differ in what they cover, the size of the deductible and/or co-payment, limits of coverage and the options for treatment available to the policyholder. Health insurance can be directly purchased by an individual, or it may be provided through an employer. Medicare and Medicaid are programs which provide health insurance to elderly, disabled, or un-insured individuals. There are a number of companies which provide private health insurance, including Blue Cross, United Healthcare, or Aetna.