A: Pre-existing conditions are defined as any injury, sickness or medical condition, for which the insured has symptoms or consulted a physician, has been hospitalized or was prescribed medications within a certain period before the effective date of coverage. The insurance company will 'look back' only so far (usually 3 months to one year) but, depending on the condition, will look back over your entire lifetime. Any pre-existing condition that has not been stable for a certain period of time will typically be excluded from coverage. That's why it's important to be able to easily compare coverage and definitions before choosing the plan that works for you.