No matter how old you are, if you have a disability that prevents you from working, you may be able to claim benefits from the Social Security Administration (SSA). There are two benefit programs you can apply for:

• Social Security Disability Insurance (SSDI): available only to disabled people who've already worked for a certain number of years.
• Supplemental Security Income (SSI): available to disabled or elderly people whose incomes and assets are very low.

Benefits include cash and medical care, and depend on which program you qualify for.

How the SSA Defines Disability

A crucial part of claiming benefits under either Social Security program is proving that you are severely disabled -- that is, that you have a physical or mental condition that prevents you from doing any substantial gainful activity and will last at least one year or will cause your death.

The determination of whether you are disabled leaves a lot of room for argument. The fact that your doctor may have advised you not to work, or that you feel too ill to work, does not necessarily mean that the SSA will agree that you are disabled.

The SSA evaluates disability using its own medical experts, based on a list of physical and mental conditions contained in its regulations. These are available on the SSA's website, at www.ssa.gov (search for "Listing of Impairments"). Be prepared: these listings are highly complex and full of medical terminology. For a version in plainer English, see Nolo's Guide to Social Security Disability , by David A. Morton III, M.D (Nolo).

The good news is that if you are denied benefits because the SSA says you are not disabled, you have a good chance of winning on appeal. Often you simply need to appear in person at a hearing and show more evidence of your disability. (To learn more about appealing social security benefit denials, read Nolo's article  Denial of Social Security Benefits: How to Appeal.)

Social Security Disability Insurance (SSDI)

To be eligible for Social Security Disability Insurance (SSDI), you must not only be disabled, but you must also have built up sufficient "work credits" with Social Security. Exactly how many credits you will need depends on your age and the year you became disabled. Twenty of your work credits must have been earned within the last ten years before you became disabled. To learn how to apply for benefits, see Social Security: How to File for Benefits.

If your application is approved, your Social Security disability benefits will include cash payments in an amount determined based on your age and your personal earnings record. Average payments range from $500 to $2,000 a month.

After collecting disability benefits for 24 months, you will become eligible for Medicare, regardless of your age. In the meantime, if your income is low, you may qualify for Medicaid.

Supplemental Security Income (SSI)

The Supplemental Security Income (SSI) program is run by the SSA, but it is actually a cooperative program between the SSA and your state government. That means that your eligibility, as well as the amount of benefits you receive, will depend on what state you live in. For federal SSA purposes, however, you must meet all of the following four criteria:

• You must be blind, disabled, or age 65 or over.
• You must be either a citizen of the United States, or meet very narrow requirements based on your U.S. permanent residency, military service, or political asylee or refugee status.
• Your monthly income must be low. Only about half of your actual income will be taken into account, but this counted income cannot be higher than an amount set by the state in which you live -- usually around $500 to $700 per month ($750 for a couple). However, some states allow people with higher incomes to receive state benefits.
• The property you own (minus certain items, such as your car and home) must be worth less than $2,000, or $3,000 for a couple. ( To learn how to apply for benefits, see Social Security: How to File for Benefits.)

If your application is approved, your SSI benefits will include cash payments at a minimum of $637 per month for an individual or $956 per month for a couple (2008). Your state may supplement this amount with an additional payment (called the State Supplementary Payment). The federal amount is adjusted in January of each year, depending on the U.S. cost of living.

You will also be eligible for Medicaid, food stamps, rehabilitation, and home care, if necessary.

To learn more about Social Security disability benefits, get  Nolo's Guide to Social Security Disability , by David A. Morton III, M.D (Nolo).