It all depends on the pre-existing condition, and the terms and conditions of the policy. Some insurance companies offer plans that cover pre-existing conditions as long as they have been stable for a certain period of time (3 to 6 months) before departure from your home country. Sometimes, pre-existing conditions will not be covered. It is important to read your entire policy to make sure you are aware of the definitions affecting coverage, as well as the possible exclusions that may apply.Only some of the available plans will cover pre-existing medical conditions such as diabetes, high blood pressure, heart conditions, etc. Other policies, while they do cover stable pre-existing medical conditions, use strict eligibility questions to screen out applicants (for example, no coverage available if you use an ICD (pacemaker), oral steroids for lung conditions, diagnosis of stroke, blood clots, congestive heart failure or heart murmur in past 12 months, etc.).