Medicare Part A (Hospital Insurance) covers blood you get as a hospital inpatient.
Medicare Part B (Medical Insurance) covers blood you get as a hospital outpatient.
Your costs in Original Medicare
If your provider gets blood from a blood bank at no charge, you won't have to pay for it or replace it. If the provider has to buy blood for you, you must either pay the provider costs for the first 3 units of blood you get in a calendar year, or you or someone else can donate the blood.