Some travel insurance plans provide coverage for pre-existing conditions. The definition of a pre-existing condition will depend on the look back period. The look back period is an amount of time in the past from the effective date. If there is any change in a previously diagnosed medical condition during the look back period, then that medical condition is considered pre-existing. A change can mean a different diagnoses, treatment, medication or even dosage. Always refer to the certificate of insurance for details.