How much GDP does Medicare take up and does it count as a part of healthcare, or a something different?

Gross Medicare outlays were 3.2% of US GDP in fiscal year 2008. Medicare part A and B covers approximately 44 million retired Americans, which comprise about 15% of the population. Spending only about 2% of total outlays on overhead costs (compared to 30-50% for private insurers), Medicare is by far the most efficient health insurance program (public or private) in the United States.