Medicare Advantage vs. Medigap: how to choose.
Both options cover the same Medicare-approved care. They work very differently — and the choice you make at 65 is harder to undo than most people realize.
At 65 you make one of the most consequential healthcare decisions of your life, often under marketing pressure during a single open enrollment window. The choice between Medicare Advantage (Part C) and Original Medicare with a Medigap supplement isn't about which is better in the abstract. It's about which is better for your specific health, finances, and risk tolerance — and which choice you can still reverse in five or ten years if you change your mind.
What you're actually choosing between
Original Medicare + Medigap: Part A (hospital) + Part B (outpatient) directly from the government, plus a Medigap supplement that covers most of the cost-sharing Original Medicare doesn't, plus a separate Part D plan for prescriptions. Higher premiums, lower out-of-pocket variability, no networks, accepted by virtually every provider in the country. Medicare Advantage: a private insurance plan that replaces Original Medicare. Usually lower or zero monthly premium, network restrictions (often HMO or PPO), copays for specific services, often includes Part D and extras like dental/vision/gym. The plan negotiates with providers; you live within its rules.
The cost math is not what marketing suggests
MA plans look cheaper because the premium is low or zero. But the out-of-pocket maximum on most MA plans is $4,000 to $8,000 per year. Medigap Plan G has a higher monthly premium but caps the out-of-pocket exposure at the Part B deductible (around $250). A healthy year: MA wins. A bad year — surgery, cancer treatment, long hospital stay — Medigap saves you thousands. The choice depends on how you want to absorb that variability.
Network matters more than people realize
MA networks vary widely by plan and by region. A plan that includes MD Anderson in Houston may not include Mayo Clinic if you need a second opinion. Specialist referrals, out-of-network coverage for travel, and continuity of care after a move all hinge on the network. Original Medicare + Medigap has no network in the same sense — any provider that accepts Medicare accepts your supplement.
The switching trap nobody warns you about
You can switch from Original Medicare to Medicare Advantage during any annual open enrollment. But switching from MA back to Original Medicare with Medigap is conditional on Medigap underwriting in most states — and Medigap insurers can deny you, charge you more, or refuse pre-existing condition coverage based on your health at the time of switch. The one-way door is real. Pick MA in good health and develop a chronic condition; getting back may be expensive or impossible. Texas does not have guaranteed-issue rules outside the initial window. Plan accordingly.
IRMAA and the higher-income surcharge
Both options are subject to IRMAA — the income-related premium surcharge on Part B and Part D. If your modified adjusted gross income from two years ago crosses a threshold, your premiums jump. MA's Part D portion is also subject. Higher-income retirees often forget this when comparing the headline premium numbers.
How I think about it for clients
Health stability and family medical history matter. Travel patterns matter. Tolerance for premium variability matters. Tolerance for prior-authorization paperwork matters. Specific providers you want to keep seeing matter. For couples, the decision can split — one MA, one Medigap — depending on each spouse's situation. There's no universal right answer. There is a careful answer.
The biggest mistake I see is treating this as a one-time decision driven by who has the friendliest broker. Run the numbers, picture a few different five-year futures, and make sure you understand the one-way door before you walk through it.