A pre-existing health condition that existed before you apply for a health insurance policy can affect your health insurance as it may not be covered. Most private medical or health insurance policies do not cover pre-existing medical conditions or illness when starting a new personal policy. A pre-existing condition is a medical condition which you are aware of or has been diagnosed and which has required medical treatment in most cases within the last five years of the commencing date of the policy. Your policy will specify the time period in which a pre-existing medical condition may become eligible for cover.
As already mentioned sometimes a health insurance policy may not cover individuals with a pre-existing condition; however impose a waiting period of usually two years before coverage may be given. If you have any doubts about this it is best to discuss it with your insurance company or broker before going ahead with a new policy.