• Medicare Advantage allows coverage through private health insurance providers.Vicky Kasala Productions/Photodisc/Getty Images
  
  Medicare Advantage, also known as Medicare Part C, provides Medicare beneficiaries with health coverage through private health insurance plans, which the Medicare program must approve. This insurance covers both ordinary medical costs (similar to Medicare Part A) and hospitalization (as in Medicare Part B). The program carries similar eligibility rules to Medicare parts A and B, the traditional Medicare programs first initiated in the 1960s.
  
  

Enrollment Period

• To enroll in Medicare Advantage, you must already carry Medicare Part A and B. For initial enrollment, you must be within the six-month Medicare eligibility period. That period begins three months before your 65th birthday, and ends three months after your 65th birthday. If you apply too early or too late, you will not be eligible.
  
  

Disability Beneficiaries

• If you are on Social Security disability, you must apply for Medicare Advantage from three months prior to three months following the 25th month of your disability, as determined by Social Security's "onset date."
  
  

Swtiching Plans

• If you intend to switch Medicare Advantage plans, the government can turn you down for applying outside of the enrollment period, which runs from November 15 through the end of the year, every year.
  
  

Employment

• The government can turn you down for not working at least 10 years in a job in which you contributed Medicare taxes (ordinarily deducted from your paycheck). This serves as a general eligibility requirement for Medicare as well as Social Security.
  
  

Residency Status

• You can also be denied for Medicare Advantage if you are not a citizen or permanent resident of the United States.
  
  

Pre-Existing Conditions

• You may join Medicare Advantage with pre-existing conditions, with the exception of end-stage renal disease.