A deductible is a specified dollar amount that you are required to pay before any emergency medical benefits will be paid.
On a comprehensive policy, if the medical benefit has a deductible it will be listed right next to the dollar amount for the medical benefit when you are viewing a quote. For the most part there is no way to adjust the deductible on a comprehensive policy, although some companies offer Medical Upgrades that may remove it.
Medical Single Trip policies are another story. All of these plans automatically include a $250 deductible when you first view them. However, on these policies the deductible is shown in the Additional Options section, towards the bottom of the quote. Here you will be offered the option to increase, decrease or remove the deductible altogether. Naturally this will affect the premium depending on which way you alter it.
Medical Multi-trip policies are more like packages in that they will always include a deductible and it cannot be removed. Similar to the Single Trip policies, this will be shown in the Additional Notes section of the quote.