There are no federal mandates requiring Medicare Supplement Plans to be available to people under the age of 65 who are on Medicare due to a disability. Nonetheless, some states require insurers to offer at least one option to those under 65. These carriers may occasionally allow you to enroll in Plan G.
Plan A is the plan most commonly available to those under the age of 65. Plan A only provides the most basic benefits. Some carriers, however, recognize the value of widespread plan availability, and will allow those on disability to enroll in Plan G.
But if you enroll in a Medicare Supplement Plan before the age of 65, your premium may be double or even triple that of someone over 65. Carriers may raise the price to account for the high medical costs associated with your disability.