She Plans to Join Costco’s New Medicare Advantage Plan at 65. Once Her 12-Month Trial Right Ends, a Medigap Insurer Could Ask Health Questions and Reject Her Application

A hypothetical Sacramento woman turning 65 in 2027 fills her prescriptions at Costco Wholesale (NASDAQ:COST) and buys her glasses there. She receives an offer for a $0-premium Medicare Advantage plan bearing the warehouse club’s name and enrolls when first eligible.

The choice feels reversible, and for 12 months it mostly is. After that, a Medigap insurer may ask about her health and charge more or turn her down.

Costco and SCAN Health Plan said they would sell jointly branded Medicare Advantage plans in two states and a Medicare supplement in a third, pending approval by the Medicare agency. The safety net described below covers only people who join Advantage when they are first eligible at 65. Most people who delayed Medicare past 65 will not have access to this trial right.

Costco’s Medicare Plans Now Have Real Markets

On Oct. 1, 2026, the companies announced SCAN Costco Medicare Advantage (HMO) for 17 California counties and two Nevada counties, with coverage starting January 1, 2027. Benefits differ by county. They may include a $0 monthly plan premium, a $300 vision allowance, a $400 allowance towards hearing aids, and preferred pricing at Costco Pharmacy. The plan does not include a Costco membership.

A $0 plan premium still leaves the Part B premium, which is $202.90 per month in 2026, up from $185. She pays that amount whichever path she picks.

Her 12-Month Trial Right

According to Medicare.gov, a person who “joined a Medicare Advantage Plan when you were first eligible for Medicare Part A at 65” can buy certain Medigap policies sold in her state if she switches back to Original Medicare within the first year. While that right lasts, a Medigap insurer cannot deny her coverage or charge more because of her health.

She can apply as early as 60 days before her Advantage coverage ends and no later than 63 days after. She was new to Medicare after January 1, 2020, so Plans C and F are off the table, and Plan G becomes the practical target. Medigap policies sold after 2005 exclude drug coverage, so she also needs to enroll in a separate Part D plan when she leaves Advantage.

What Happens After the First Year

The federal guarantee ends in month 13. In most states, a Medigap insurance company can then review her medical records and either charge more or refuse coverage. Medicare.gov cautions that some people who leave Advantage may not be able to get any Medigap policy. A new diagnosis in her second year, such as cancer or a heart condition, could make Medigap harder to secure.

State “birthday rules” won’t help her. Those rules apply to people who already have a Medicare Supplement policy. California’s birthday rule gives existing Medigap policyholders at least 60 days to switch to a policy with equal or lesser benefits. Someone leaving Advantage does not qualify. A few federal rights do last, such as when a plan is changing or ending in her area. A handful of states go further, so she should check with her own state insurance department before counting on any exception.

What She Should Compare Before Enrolling

In a healthy year, the Advantage plan costs her less. A sick year looks different. Her costs rise toward the plan’s in-network maximum, which does not count Part D drug spending or out-of-network care. Meanwhile, under an HMO, Advantage plans may need her to stay in network and get approval for some drugs or services. With Plan G, a bad year costs her about the $283 Part B deductible plus her premiums.

For a healthy 65-year-old whose doctors are all in SCAN’s network, the Costco plan is a reasonable first year. If she has a chronic condition, sees an out-of-network specialist, or spends winters elsewhere, Original Medicare plus Plan G may be worth considering from the start. For her, the trial right can run out before she finds out she needs it. (IRMAA surcharges and other premium traps can silently change either choice, which is why we mapped the full set in a free Medicare guide.)

Moves to Make Before Month 12

• Confirm the network before you sign. Look up every doctor and hospital you use in SCAN’s directory. Then get the plan’s Evidence of Coverage and read the in-network out-of-pocket maximum and the prior authorization list.
• Get a Plan G quote at 65 and again around month 9. The second quote from a Medigap insurer shows what Plan G would cost while she still has the right to buy it without health questions.
• Set a calendar reminder for month 10. If you want to leave, file the Medigap application inside the window that opens 60 days before your Advantage coverage ends, and pick a Part D plan at the same time.

A Costco-branded plan comes with the same Medicare enrollment rules as any other Advantage plan. The 12-month clock starts when her coverage begins.

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