What CMS (Centers for Medicare and Medicaid Services) Actually Does

CMS is the federal agency that runs Medicare, Medicaid, and the health insurance marketplaces

CMS — the Centers for Medicare and Medicaid Services — is the part of the U.S. Department of Health and Human Services that administers Medicare, Medicaid, and the health insurance marketplaces where you can buy private coverage. It does not make policy or set law; Congress does that. CMS runs the programs Congress created, pays the claims, sets the rules for how hospitals and doctors get paid, and handles the day-to-day operation of the largest health insurance system in the country.

If you have Medicare, your claims go through CMS systems. If you are on Medicaid, your state runs the program but CMS sets the federal standards and funds part of it. If you bought insurance on Healthcare.gov, that marketplace is run by CMS. When you call Medicare, you are reaching a CMS contractor. When your doctor's office submits a bill to Medicare, it goes to a CMS-contracted claims processor.

Understanding what CMS does matters because it explains why certain rules exist, where to find official information, and who actually handles your claim or payment. CMS is not a health insurance company itself — it does not employ doctors or own hospitals. It is the government office that pays for care and enforces the rules.

Key Takeaways

• CMS runs Medicare, Medicaid, and Healthcare.gov, meaning it sets the rules and pays the bills for these programs.
• CMS does not make laws — Congress does — but it writes the detailed regulations that explain how those laws work in practice.
• Most CMS work is done through contractors: insurance companies process claims, call centers answer questions, and state agencies run Medicaid.
• The official CMS website (Medicare.gov for Medicare questions, Medicaid.gov for Medicaid) is where to find authoritative information and contact details.
• CMS also oversees quality standards for nursing homes, hospitals, and other providers that receive Medicare or Medicaid money.

The three main programs CMS runs

Medicare is the federal health insurance program for people 65 and older, some younger people with disabilities, and people with end-stage renal disease. CMS sets the benefit rules (what is covered, what you pay), pays the claims, and contracts with private insurance companies to process those claims and handle customer service.

Medicaid is a joint federal and state program for low-income people. CMS provides federal funding and sets minimum standards, but each state designs its own program, sets its own income limits, and decides which services to cover beyond the federal minimum. This is why Medicaid rules differ sharply from state to state.

The Health Insurance Marketplaces (Healthcare.gov and state-run equivalents) are where people who do not have employer coverage or Medicare can buy private health insurance. CMS runs the federal marketplace and oversees the state marketplaces. It also administers subsidies and tax credits that reduce premiums for people who meet income requirements.

How CMS actually operates day-to-day

CMS does not directly answer your phone call or process your claim. Instead, it contracts with private companies and state agencies to do that work. When you call Medicare with a question, you reach a call center run by a contractor under CMS supervision. When your doctor submits a bill to Medicare, it goes to a claims processor — usually a private insurance company like Anthem or Humana — that CMS hired to handle that work.

This matters because it means the person helping you works for a contractor, not directly for CMS, but they are following CMS rules and their work is overseen by CMS. If you have a problem with how your claim was handled, you can appeal through CMS processes even though the contractor made the initial decision.

CMS also works with state Medicaid agencies. Each state runs its own Medicaid program, but CMS approves the state's plan, monitors whether it meets federal standards, and provides the federal funding. CMS can withhold money or require changes if a state is not following the rules.

What CMS regulates beyond just paying claims

CMS sets and enforces standards for any healthcare provider that receives Medicare or Medicaid money. This includes hospitals, nursing homes, home health agencies, dialysis centers, and hospices. CMS inspectors visit these facilities, check whether they meet safety and quality standards, and can fine or shut down providers that do not comply.

CMS also publishes data on hospital quality, nursing home inspections, and provider performance. Websites like Care Compare (for nursing homes) and Hospital Compare are CMS tools that let you see inspection results and safety records. This information comes from CMS oversight, not from the providers themselves.

Additionally, CMS sets the payment rates that Medicare pays doctors, hospitals, and other providers. These rates change each year and are published in the Federal Register. Providers must accept Medicare's payment rate or not treat Medicare patients.

Where to find official CMS information

The main CMS website is CMS.gov, but it is designed for healthcare professionals and policy people, not for patients. For Medicare questions, go to Medicare.gov. For Medicaid, go to Medicaid.gov, which links to your state's Medicaid program. For marketplace insurance, go to Healthcare.gov.

These three sites are the official sources for benefit information, coverage rules, and how to contact your program. If you see conflicting information elsewhere, check these sites first. They are updated when rules change and they reflect what CMS actually requires.

You can also contact CMS directly through these sites, though for most questions you will be routed to a contractor. Medicare.gov has a phone number for Medicare questions. Medicaid.gov links to your state agency. Healthcare.gov has a phone line for marketplace questions.

Why CMS rules matter to you

CMS rules determine what Medicare covers, what you pay out of pocket, which doctors and hospitals are in your network, and how claims are processed. If you disagree with a coverage decision or claim denial, you appeal through CMS processes. If you think a provider violated CMS standards, you can file a complaint with CMS.

CMS also sets important date. For example, CMS rules say you have a certain window to enroll in Medicare or face a penalty. CMS rules say you have 60 days to appeal a claim denial. CMS rules say nursing homes must give you 30 days' notice before discharge. These important date are not suggestions — they are federal requirements.

Understanding that CMS is the authority behind these rules helps you know where to go when you have a problem. If your claim was denied, you appeal to CMS (through its contractor). If your doctor's office says something is not covered, you can check Medicare.gov to verify. If a nursing home is not following the rules, you report it to CMS.

The difference between CMS and other health agencies

CMS is often confused with other federal health agencies. The FDA (Food and Drug Administration) approves drugs and medical devices. The CDC (Centers for Disease Control) tracks disease and public health. The NIH (National Institutes of Health) funds medical research. CMS does none of these things — it pays for healthcare and enforces rules for providers.

CMS is also separate from your state's insurance commissioner, who regulates private health insurance companies. CMS regulates the programs it runs (Medicare, Medicaid, marketplaces) and the providers that receive CMS money. Your state insurance commissioner regulates other insurance products.

If you have a complaint about a private insurance company's customer service or claim handling, you may file with your state insurance commissioner. If you have a complaint about how Medicare or Medicaid handled your claim, you file with CMS.

Frequently Asked Questions

Is CMS the same as Medicare?

No. CMS is the government agency that runs Medicare, Medicaid, and the marketplaces. Medicare is one of the programs CMS operates. CMS also runs two other major programs, so it is larger than Medicare alone.

Can I contact CMS directly with a problem?

You can reach CMS through Medicare.gov, Medicaid.gov, or Healthcare.gov, depending on which program you use. Most routine questions and complaints are handled by contractors, but your case is tracked in CMS systems. For appeals and formal complaints, CMS has specific processes outlined on these websites.

Does CMS decide what my doctor can prescribe?

No. Your doctor decides what to prescribe. CMS decides whether Medicare or Medicaid will pay for it. If CMS does not cover a drug your doctor prescribes, you can pay out of pocket, ask your doctor for an alternative that is covered, or request an exception through an appeals process.

Why do Medicaid rules differ from state to state if CMS runs it?

CMS sets federal minimum standards and provides funding, but Congress designed Medicaid as a partnership between the federal government and states. Each state has flexibility to set its own income limits, choose which optional services to cover, and design how the program works. CMS approves state plans and ensures they meet federal standards.

Where do I report a problem with a nursing home?

You can file a complaint with CMS through Medicare.gov or by contacting your state's Medicaid agency or nursing home ombudsman. CMS investigates complaints about safety and quality standards. Your state ombudsman can also advocate on your behalf and help you understand your rights.