Medigap can cover the gaps in Original Medicare, but timing rules matter. Here is how San Diego seniors compare plans and use California's birthday rule.
By Marcus Reyes, LSW · October 17, 2026
Original Medicare pays for much of a senior's hospital and doctor costs, but it leaves real gaps: deductibles, a 20 percent coinsurance on most outpatient care, and daily copays in a long hospital or skilled nursing stay. Medigap, also called Medicare Supplement insurance, is a private policy that pays some or all of those leftover costs. It works only alongside Original Medicare, and it is sold separately from a Medicare Advantage plan. You cannot have both at once.
Medigap does not cover long-term custodial care, so it will not pay for assisted living, memory care, or a caregiver who helps with bathing and dressing. It also does not include prescription drug coverage, which comes from a separate Part D plan. For many San Diego families, the real value of Medigap is predictability: a parent with a hospital stay or a rehab admission faces far fewer surprise bills. If your parent is weighing this choice against a Medicare Advantage plan, our comparison of Medicare Advantage and Original Medicare walks through the tradeoffs.
Medigap plans are standardized by letter, and a Plan G in San Diego offers the same basic benefits as a Plan G anywhere else in the country. That makes shopping simpler than it looks. What differs between insurers is the monthly premium, how the insurer raises rates over time, and the company's customer service. Plan G and Plan N are the plans most often discussed today. Plan F is generally available only to people who became eligible for Medicare before 2020.
When you compare quotes, ask whether the premium is priced by issue age, attained age, or community rating, because that determines how quickly it climbs as your parent gets older. A lower premium at 65 can become the more expensive choice by 80. Also look at how often the company has raised rates in recent years. The California Department of Insurance publishes Medigap shopping information, and the federal Medicare Plan Finder at 1-800-MEDICARE (1-800-633-4227) lists plans available by zip code.
Timing is the part families most often miss. When a person is 65 or older and first enrolled in Medicare Part B, a six-month Medigap open enrollment period begins. During that window, insurers must sell you any plan they offer, regardless of health history, and cannot charge more for existing conditions. After the window closes, most insurers in most states can use medical underwriting, which means a parent with diabetes, heart disease, or a recent hospital stay may be turned down or charged more.
California has a helpful exception often called the birthday rule. For a limited time around each birthday, a senior who already has a Medigap plan can switch to another plan of equal or lesser benefits from a different insurer without answering health questions. Check the exact window and eligibility with the California Department of Insurance or HICAP before relying on it, because insurers must notify members and the details matter. This rule is a way to lower premiums when a rate increase arrives, not a way to move up to richer benefits.
You do not need a broker to sort this out, and unbiased help is available at no cost. HICAP, the Health Insurance Counseling and Advocacy Program, offers free, one-on-one Medicare counseling in San Diego County through trained volunteers and staff. You can reach the statewide line at 1-800-434-0222. Aging & Independence Services, the county's Area Agency on Aging, can also connect you with local resources at 1-800-339-4661.
If your parent is on Medi-Cal as well as Medicare, a Medigap policy is usually unnecessary because Medi-Cal helps cover many cost-sharing amounts. Before spending money on a supplement, confirm with HICAP what coverage your parent already has. And if a parent is considering a move to assisted living, remember that Medigap will not pay for that care, which is why many families review their long-term care funding at the same time.
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