What CMS Is and How It Connects Medicare and Medicaid

CMS is the federal agency that runs Medicare and Medicaid

CMS stands for the Centers for Medicare & Medicaid Services. It is a division of the U.S. Department of Health and Human Services, and it is the single federal agency responsible for running both Medicare and Medicaid. If you receive Medicare benefits or Medicaid coverage, CMS is the organization behind the scenes managing your program, setting the rules, and paying the claims.

CMS does not deliver care itself — doctors, hospitals, and insurers do that. Instead, CMS sets policy, manages the money, and makes sure the programs follow federal law. When you call Medicare with a question about your benefits, you are reaching a CMS contractor. When your state Medicaid office processes your paperwork, they are following CMS guidelines.

Understanding CMS matters because it is where policy changes start, where you can find official information, and where complaints about your coverage eventually go if your state program does not resolve them.

Key Takeaways

CMS is the federal agency that operates both Medicare and Medicaid, though each program has different rules and covers different groups of people.
Medicare is a federal program for people 65 and older, some younger people with disabilities, and people with end-stage renal disease; Medicaid is a joint federal-state program for low-income individuals and families.
CMS sets the rules for both programs, manages the federal funding, and oversees state Medicaid programs to may support they meet federal standards.
The official CMS website (Medicare.gov for Medicare questions and Medicaid.gov for state programs) is where to find authoritative information about coverage, costs, and enrollment.
If you have a problem with your Medicare or Medicaid coverage, CMS has a formal appeals process, and you can file a complaint with CMS if your state or plan does not resolve it.

How CMS runs Medicare differently from Medicaid

Although CMS runs both programs, they work very differently. Medicare is entirely federal — the same rules explore everywhere, and the federal government pays for it through payroll taxes and premiums. You become may be able to access for Medicare when you turn 65, regardless of your income or where you live. CMS sets the benefit structure, decides what is covered, and determines how much you pay in premiums and deductibles.

Medicaid is a partnership between the federal government and each state. The federal government provides funding and sets minimum standards, but each state designs its own program within those guidelines. This means Medicaid coverage, income limits, and what you pay vary significantly from state to state. CMS approves each state's Medicaid plan and monitors whether the state is following federal rules.

Because of this difference, if you move from one state to another, your Medicare coverage stays the same, but your Medicaid coverage may change completely — or you may no longer may have access to at all.

What CMS actually does day-to-day

CMS manages the infrastructure that keeps both programs running. For Medicare, CMS contracts with private insurance companies to process claims, handle customer service calls, and send out payment checks. CMS sets the rates these contractors must follow and audits their work. When you call the Medicare phone line, you reach a CMS contractor, not CMS directly.

For Medicaid, CMS works with state agencies. Each state has its own Medicaid office that determines who qualifies, processes paperwork, and manages the day-to-day program. CMS reviews the state's decisions to make sure they follow federal law, provides funding, and can take action if a state is not meeting federal standards.

CMS also runs the enrollment systems — Medicare.gov for Medicare sign-ups and the Healthcare.gov marketplace for people who need private insurance. It publishes the official rules, updates coverage policies, and maintains the databases that track who is enrolled in what program.

Where to find official CMS information

CMS maintains two main public websites. Medicare.gov is the official source for Medicare information, including what is covered, how much things cost, how to enroll, and how to appeal a coverage denial. You can search for providers, compare plans, and find your local Medicare office.

Medicaid.gov is the federal Medicaid site, but it does not process applications or determine your may be able to access. Instead, it directs you to your state's Medicaid program, which is where you actually explore and find out what your state covers. Each state's Medicaid office has its own website and phone number.

If you need to contact CMS directly — for example, to file a complaint about how your state Medicaid program treated you — you can reach the CMS Office of Beneficiary Protections through Medicare.gov or by calling 1-800-MEDICARE (1-800-633-4227).

CMS and appeals: what happens when coverage is denied

When Medicare or Medicaid denies a claim or refuses to cover a service, CMS has set up a formal appeals process. For Medicare, you have the right to appeal directly to CMS if your plan or provider denies coverage. The appeal goes through levels: first a reconsideration by the plan, then an independent review, then a hearing before an administrative law judge if the amount in dispute is large enough.

For Medicaid, the appeals process is run by your state, but it must follow CMS federal standards. If your state denies you coverage or terminates your benefits, you have the right to a hearing. If you believe your state is not following federal Medicaid rules, you can file a complaint with CMS, which can investigate and require the state to correct the problem.

CMS also oversees the quality of care in both programs. If you have a complaint about the quality of medical care you received, or if you believe a provider committed fraud, you can report it to CMS.

Why CMS policy changes matter to you

CMS updates its policies regularly, and these changes affect what you pay and what is covered. For example, CMS decides whether a new drug or treatment is covered by Medicare, what the annual deductible will be, and whether your copay for a specific service will go up or down. These decisions are published in the Federal Register and on Medicare.gov, usually well in advance of when they take effect.

If you receive Medicaid, CMS policy changes can also affect you indirectly. When CMS changes federal Medicaid rules, states must update their programs to match. This might mean your income limit changes, new services become covered, or your copay structure shifts.

Staying informed about CMS announcements — especially during the annual Medicare open enrollment period in the fall — helps you understand changes to your coverage and make decisions about your plan.

Frequently Asked Questions

Is CMS the same as Medicare?

No. CMS is the federal agency that runs Medicare. Medicare is the health insurance program itself. Think of CMS as the organization and Medicare as the product. CMS also runs Medicaid, which is a different program with different rules and may be able to access.

Can I contact CMS directly if I have a problem with my Medicare plan?

You can reach CMS through Medicare.gov or by calling 1-800-MEDICARE. However, your first step should usually be to contact your Medicare plan or provider directly, since they handle most day-to-day issues. CMS gets involved if your plan does not resolve the problem or if you want to file a formal appeal or complaint.

Does CMS determine if I may have access to for Medicaid?

No. Your state's Medicaid office determines your may be able to access based on your income, family size, and other factors. CMS sets the federal rules that states must follow, but each state makes its own may be able to access decisions. You explore through your state, not through CMS.

What should I do if I think CMS made a mistake with my Medicare benefits?

Start by contacting your Medicare plan or provider to ask why the decision was made. If you disagree, you have the right to appeal. You can request an appeal through your plan, and if you are not satisfied with their response, you can ask for an independent review. CMS oversees this entire process.

Where do I find out about changes to Medicare coverage?

Medicare.gov publishes all coverage changes, usually in the fall before they take effect on January 1. You can also call 1-800-MEDICARE to ask about specific services or drugs. Your Medicare plan is required to send you a notice of changes each year.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.