Low-income Subsidy – Eligible beneficiaries who have limited income may qualify for a government program that helps pay for Medicare Part D prescription drug costs.
Medicare beneficiaries receiving the low-income subsidy (LIS) get assistance in paying for their Part D monthly premium, annual deductible, coinsurance, and copayments. Also, individuals enrolled in the Extra Help program do not have a gap in prescription drug coverage, also known as the coverage gap, or the Medicare “donut hole.” The amount of subsidy depends on the individual’s income compared to the Federal Poverty Level and resource limitations set by the Social Security Act.
Further reading –
https://kaiserfamilyfoundation.files.wordpress.com/2013/01/8094.pdf