Medicare beneficiaries under age 65 do not have the same federal protections that are granted to people 65 and older when buying Medigap insurance. Instead, the rules are left to each state. Therefore, to what extent Medigap is available or affordable to you, as a younger beneficiary, depends on the law in the state where you live.
In many states, insurance companies are not required to sell any Medigap policies to you. Some states require one or two policies to be made available. Most states allow insurers to take your health status and preexisting medical conditions into account when determining your premium, which can greatly push up the cost. But a few state laws do better — insisting, for example, that people with Medicare due to disability must receive the same protections that federal law provides for people 65 and older. To check out the law in your own state, contact the state department of insurance; for contact information go to http://www.naic.org/state_web_map.htm and select your state.
If you are unable to buy a Medigap policy right now, or only one that charges you very high premiums, remember that when you turn 65, the clock will be reset. You will then be eligible for Medicare based on age instead of disability, and you will be able to buy any Medigap policy of your choice with full federal protections — provided that you buy one within six months of your 65th birthday, unless you happen to live in one of the few states that allow you to buy Medigap at any time.