Medicare in Missouri

Medicare in Missouri follows the same federal rules as everywhere else, but the state adds one meaningful twist: the Missouri Anniversary Rule. Each year, for a 30-day window starting on the anniversary of your Medicare Supplement (Medigap) policy, you can switch to the same lettered plan with a different insurance carrier without answering health questions. That single rule makes Missouri one of the more forgiving states for shopping Medigap premiums year after year, since most states only guarantee that kind of no-underwriting switch during your initial 6-month Medigap Open Enrollment Period.

Roughly 1.3 million Missouri residents are enrolled in Medicare, according to enrollment data from the Centers for Medicare & Medicaid Services (CMS), the federal agency that administers Medicare. Missourians choose among Original Medicare (Parts A and B, run directly by the federal government), Medicare Advantage (a private-plan alternative that often bundles extra benefits like dental or vision into one plan), and Medicare Supplement, also called Medigap (a standardized policy sold by private insurers to cover costs Original Medicare leaves behind). Carriers active in the state include UnitedHealthcare, Humana, Aetna, Anthem Blue Cross Blue Shield, Cigna, WellCare, and others, depending on your county.

Missouri Medicare quick facts (2026)

• Medicare beneficiaries: Roughly 1.3 million Missouri residents are enrolled in Medicare.
• Active Medicare Advantage carriers: UnitedHealthcare, Humana, Aetna, Anthem Blue Cross Blue Shield, Cigna, WellCare, and others, depending on county.
• State Medicaid program: MO HealthNet, Missouri's Medicaid program, which coordinates with Medicare for dual-eligible residents through Dual Eligible Special Needs Plans (D-SNPs), a type of Medicare Advantage plan built for people who qualify for both Medicare and Medicaid.
• State quirk: The Missouri Anniversary Rule applies to Medigap only. Medicare Advantage and Part D changes still follow the federal enrollment calendar.

Medicare basics in Missouri

Medicare is a federal health insurance program, so eligibility rules, enrollment periods, and plan types are the same in Missouri as in every other state. What differs is which specific plans are available to you: premiums, provider networks, and extra benefits vary by ZIP code and county within Missouri.

Most Missouri residents become eligible for Medicare at age 65, typically through Social Security. For the full 7-month enrollment window around your 65th birthday, see our guide on turning 65 and Medicare enrollment.

What Missouri residents typically compare

Medicare Advantage. Many Missouri counties have 20-50 or more Medicare Advantage plans to choose from, with premiums, provider networks, and extras that vary by county and carrier.

Medicare Supplement (Medigap). Medigap plans are federally standardized, meaning a Plan G from one carrier covers the same benefits as a Plan G from another. What varies by state and carrier is the premium and, outside guaranteed-issue windows, the underwriting rules. This is where Missouri's Anniversary Rule matters most.

Part D prescription drug plans. Standalone Part D plans are available statewide, but each plan sets its own formulary (the list of covered drugs) and network of preferred pharmacies, so the same plan can cost very differently depending on the medications you take.

For a side-by-side breakdown of these paths, see Medicare Advantage vs. Medicare Supplement.

Missouri Medicare enrollment timing

The federal Medigap Open Enrollment Period is the same in every state: it runs for 6 months starting the month you turn 65 and are enrolled in Medicare Part B. During that window, insurers cannot use medical underwriting to deny you a policy or charge more based on health conditions.

Outside that 6-month window, Missouri allows Medigap carriers to use medical underwriting, the same as most states, except during your annual 30-day Anniversary Rule window or a federal guaranteed-issue event, such as losing employer coverage.

According to Medicare.gov, the Annual Enrollment Period for changing Medicare Advantage or Part D plans runs October 15-December 7, 2026, nationwide. For a full breakdown of what you can and cannot change during this window, see our Medicare Annual Enrollment Period guide. For Missouri-specific questions about your rights during enrollment, Missouri's State Health Insurance Assistance Program (SHIP) offers free, unbiased counseling.

How to compare Medicare plans in Missouri

Because plan availability and pricing vary so much within the state, compare every plan you consider using the same criteria, including out-of-pocket maximumsstar ratings, and prior authorization rules.