Medicare spending was about $874 billion in FY2024 — roughly 13% of all federal outlays. The program covers about 67 million Americans (people 65+ and certain younger people with disabilities or end-stage renal disease) and is organized into three main parts: Part A covers hospital care, Part B covers physician and outpatient services, and Part D covers prescription drugs. Part C (Medicare Advantage) is a private-plan alternative funded through Parts A and B rather than a separate funding stream.
Only Part A — the Hospital Insurance Trust Fund — is funded by the 1.45% FICA Medicare payroll tax (matched 1.45% by your employer for 2.9% total). That's about $420 billion of the total. Parts B and D are funded mostly by general federal revenues (around 75%) plus beneficiary premiums (around 25%). When you pay your Medicare payroll tax, it goes specifically to Part A; the rest of Medicare is paid for by everyone's income tax and by retirees' monthly premiums.
Important caveat on the numbers below: budget-function outlays are reported NET of beneficiary premiums and other offsetting receipts. Gross Medicare spending by part is higher than what's shown here. CMS reports gross 2024 spending of roughly Part A $422B, Part B $553B, and Part D $146B (about $1.12T total). The federal government's net outlay is lower (~$874B) because the ~$240B of premiums beneficiaries pay for Parts B and D get netted out on the spending side. The Part B and Part D rows below show the net federal share, not the gross program cost — that's why the numbers may look smaller than figures you'd find on CMS or USAFacts.
Private plan sponsors deliver large shares of Parts C and D. UnitedHealth Group is the single largest recipient of federal Medicare dollars (Medicare Advantage + Part D plus Optum services). Humana, CVS Aetna, and Elevance Health are the other major Medicare Advantage and Part D plan sponsors. Traditional Medicare (fee-for-service) payments flow directly to hospitals, physicians, and outpatient providers — HCA, Tenet, and Community Health are among the largest hospital-chain recipients of Part A inpatient fee-for-service dollars.