There are 4 parts of Medicare, hospital insurance (part A) and medical insurance Part B helps protect people 65 and over from the high cost of health care. Part C is known as Medicare Advantage. It's an alternative to Parts A and B that bundles several coverage types, including Parts A, B, and usually D. Part D helps cover prescription drug costs. You must sign up for Part A or Part B before enrolling in Part D. Disabled people under 65 who have been entitled to Social Security Disability benefits for 24 or more months and insured workers and their dependents who need dialysis because of a permanent kidney failure also have Medicare protection. Medicare helps pay the cost of inpatient hospital services, and certain other medical items and services not covered by hospital insurance.