This category is separate from Medicare, which has its own budget function (570). Function 550 'Health' covers federal health spending outside Medicare — including Medicaid, ACA marketplace subsidies, federal health research, public health, and federal employee + military retiree health benefits.
Total spending was about $912 billion in FY2024. The biggest line by far is Medicaid (~$616B in federal matching dollars), which routes through every state's Medicaid agency and is then paid to providers and managed-care organizations (UnitedHealth Community Plan, Centene, Molina, Elevance) downstream.
Other major pieces: ACA Premium Tax Credits (~$98B) paid directly to private insurers on behalf of marketplace enrollees; Federal Employees Health Benefits Program (FEHBP) plus TRICARE for Life for military retirees (~$76B combined); NIH research grants (~$48B) flowing mostly to universities (Harvard, Johns Hopkins, UCSF, Stanford); the Indian Health Service (~$9B); HRSA-funded community health centers (~$8B); and the CDC (~$11B).
Smaller but recognizable agencies in this function include the FDA (drug, device, food, and tobacco regulation), SAMHSA (substance abuse and mental health services), and AHRQ (healthcare research quality).