What Are the US Centers for Medicare and Medicaid Services?
The US Centers for Medicare and Medicaid Services (CMS) is the federal agency within the Department of Health and Human Services that runs Medicare, Medicaid, the Children's Health Insurance Program, and the Health Insurance Marketplace. CMS sets the rules, collects payments, and oversees compliance for these programs, which together cover roughly one in three Americans. Its work affects hospitals, insurers, nursing homes, and the millions of beneficiaries who rely on these programs for care.
More from this site
Keep reading the latest coverage
What CMS Covers
CMS administers coverage for a wide range of services across its major programs. The specifics vary by program, eligibility rules, and state implementation.
- Inpatient and outpatient hospital care
- Physician and clinical services
- Prescription drugs through Medicare Part D and Medicaid
- Skilled nursing facility and home health care
- Long-term services and supports for people with disabilities
- Preventive services, screenings, and vaccinations
- Mental health and substance use disorder treatment
- Dental, vision, and hearing services under certain Medicaid plans
How CMS Is Organized
CMS operates through several centers and offices that handle policy, operations, and oversight. The agency sets payment rates, publishes coverage rules, and runs data systems that track claims and quality measures. CMS also works with state Medicaid agencies, insurance companies, and health care providers to ensure programs run according to federal standards. Because Medicaid is state-federal partnership, CMS provides guidance and funding while states manage day-to-day eligibility and benefits within broad federal parameters.
CMS and Medicare
For Medicare, CMS manages Parts A, B, C, and D. It determines which services are covered, sets premium and deductible amounts, and runs quality initiatives such as the Star Ratings system for Medicare Advantage and Part D plans. CMS also oversees the Medicare Savings Programs and the Extra Help program for low-income beneficiaries, working with states to enroll eligible people.
CMS and Medicaid
In Medicaid, CMS establishes federal requirements for eligibility, benefits, and provider payments while allowing states flexibility to design their programs within those rules. CMS approves state plan amendments, oversees waivers that let states test new delivery and payment models, and distributes federal matching funds. The agency also sets rules for managed care organizations that serve Medicaid beneficiaries in many states.
How CMS Shapes Health Care Costs and Access
CMS payment policies influence how providers are reimbursed and, by extension, what services are available to beneficiaries. Changes in Medicare reimbursement rates can affect whether physicians accept Medicare patients. Medicaid payment levels shape provider participation in states. CMS also runs quality and value-based purchasing programs aimed at improving outcomes while controlling costs, such as the Hospital Value-Based Purchasing Program and the Merit-Based Incentive Payment System for clinicians.
How Beneficiaries Interact With CMS
Most people do not contact CMS directly. Instead, they interact through Medicare, Medicaid, or their state insurance marketplace. CMS provides public resources including Medicare.gov, Medicaid.gov, and the 1-800-MEDICARE helpline. These tools help beneficiaries compare plans, find providers, understand costs, and file grievances. CMS also publishes data on facility quality, hospital readmissions, and patient satisfaction that can guide care decisions.
Key Data and Oversight Functions
CMS collects and publishes extensive data on health care spending, utilization, and quality. The agency enforces rules against fraud, waste, and abuse through its Center for Program Integrity. CMS also oversees the Federal Insurance Contributions Act tax that funds Medicare, and it administers the Recovery Audit Contractor program aimed at correcting improper payments.
Recent Policy Trends
CMS has expanded telehealth coverage in Medicare, tested direct contracting models for primary care, and pushed for value-based payment arrangements that reward quality over volume. The agency continues to work on lowering prescription drug costs, improving the user experience for Medicare plan shopping, and strengthening the infrastructure that supports electronic health records and data sharing across programs.
Why CMS Matters to You
Whether you are enrolled in Medicare, Medicaid, or a Marketplace plan, CMS shapes the rules that determine what is covered, how much you pay, and the quality standards your providers must meet. Understanding CMS helps you navigate coverage, compare options, and make informed decisions about your care.