Some travel insurance plans offer coverage for pre-existing conditions. What defines a pre-existing conditions depends on the look back period for that policy. The look back period is a set amount of time in the past from the policy effective date. If a medical condition has been completely stable during the look back period, then it is not considered pre-existing. This means that there has been no change in diagnosis, treatment, medication, prescription or dosage. Always refer to the certificate of insurance for details.