AARP Medicare Supplement vs. Advantage: What Members Should Compare

How the Two Paths Differ

AARP Medicare Supplement (Medigap) policies work alongside Original Medicare, filling gaps in deductibles and coinsurance, while Medicare Advantage (Part C) replaces Original Medicare with an HMO or PPO network run by a private insurer. Both are offered through UnitedHealthcare, but the trade-offs are structural: Medigap gives you freedom to see any Medicare-accepting doctor, while Advantage plans trade that freedom for often lower premiums and extra benefits like vision or hearing. Choosing between them depends on how much flexibility and predictability you want in your care.

Coverage and Cost Structure

With a Medicare Supplement plan, you typically pay the Part B deductible and a monthly premium on top of your Part B premium. In return, the plan covers the cost-sharing that Original Medicare leaves behind, and your out-of-pocket exposure is usually capped by the plan's benefit limits. Medicare Advantage plans generally bundle Part A, Part B, and often Part D into one monthly premium, and many include an annual out-of-pocket maximum. However, Advantage plans may require prior authorization or referrals, and coverage is limited to the plan's network except in emergencies.

What to Check in Each Plan Type

• Medigap: Confirm the plan letter (e.g., G or N), the monthly premium trend, and whether the plan is guaranteed renewable.
• Medicare Advantage: Review the provider network, prior-authorization rules, the annual out-of-pocket maximum, and whether prescription drug coverage is included or needs a separate Part D plan.

Provider Flexibility and Access

One of the clearest differences is where you can receive care. A Medigap policy allows you to walk into any hospital or specialist that accepts Medicare, which matters if you travel frequently or want to keep a longtime doctor. Medicare Advantage plans usually restrict you to in-network providers, and some require you to choose a primary care physician or get referrals for specialists. A few plans offer out-of-network benefits, but those often come with higher cost-sharing.

Enrollment Windows and Switching

The safest time to buy a Medigap policy is during your six-month Medigap Open Enrollment Period, which starts the first month you are 65 or older and enrolled in Part B. During that window, insurers cannot use medical underwriting. Switching from a Medicare Advantage plan to a Medigap policy later can involve underwriting and may be denied based on health history. If you are already in an Advantage plan, check its annual enrollment period to switch plans or return to Original Medicare with a separate Medigap and Part D policy.

Questions to Ask Before You Enroll

Before choosing, ask how the plan handles out-of-network care, whether your current doctors are in network, what the total annual cost will be (premiums plus expected cost-sharing), and whether the plan covers the services you use most often. For Medigap, confirm the plan letter and that the policy is standardized. For Advantage plans, review the evidence of coverage and summary of benefits for the year ahead. AARP's plan comparison tools can help you line up the specific options available in your ZIP code.