Turning 65 brings a wave of new vocabulary: Original Medicare, Medicare Advantage, Medigap, Part D. It’s a lot to absorb at once, and one of the most common points of confusion is where Medicare Supplement plans—also called Medigap—fit into the picture. Here’s a straightforward look at what they do and why so many people choose to add one.

What Original Medicare Doesn’t Cover

Original Medicare (Parts A and B) covers a substantial amount of hospital and medical care, but it isn’t complete coverage. It generally pays 80% of approved costs for outpatient care, leaving the remaining 20% to you—with no cap on how high that 20% can climb. There are also deductibles, hospital coinsurance for longer stays, and no built-in limit on out-of-pocket spending.

For someone who ends up with a serious illness, a major surgery, or an extended hospital stay, that uncapped 20% can add up to a genuinely large bill. Medicare Supplement plans exist specifically to fill that gap.

How Medigap Plans Work

A Medicare Supplement plan is a separate policy, sold by private insurance companies, that works alongside Original Medicare. Depending on the plan letter you choose (Plan G and Plan N are among the most popular currently available to new enrollees), the policy covers some or most of the costs Original Medicare leaves behind—coinsurance, copayments, and in some cases deductibles.

One of the most appealing features is predictability. With a solid Medigap plan, many people find their healthcare costs become far more consistent from month to month and year to year, since the plan absorbs the variable costs that would otherwise fall on them.

Freedom to See Any Provider Who Accepts Medicare

Unlike Medicare Advantage plans, which typically operate with provider networks similar to an HMO or PPO, Medicare Supplement plans work anywhere Original Medicare is accepted. There are no networks, no referrals, and no prior authorizations to navigate. If you travel frequently, split time between two states, or simply want the freedom to see any specialist without jumping through hoops, this is often the deciding factor.

Guaranteed Renewability

As long as you pay your premium, a Medicare Supplement policy cannot be canceled by the insurance company because you get sick or file claims. This matters more than it might sound—health can change quickly, and knowing your coverage won’t be pulled out from under you at the moment you need it most provides real peace of mind.

The Trade-Off: Premiums

Medigap plans generally come with a monthly premium in addition to your Part B premium, and that premium is usually higher than what you’d pay for a Medicare Advantage plan, which often has a $0 premium. This is the central trade-off in Medicare planning: Medicare Advantage tends to cost less upfront but comes with networks and variable out-of-pocket costs; Medigap tends to cost more upfront but offers predictability and provider freedom.

Neither approach is universally “better.” The right choice depends on your health, your budget, how often you expect to need care, and how much you value flexibility versus lower monthly costs.

Timing Matters

One detail that trips people up: the best time to enroll in a Medigap plan is during your six-month Medicare Supplement Open Enrollment Period, which begins the month you turn 65 and are enrolled in Part B. During this window, you generally can’t be denied coverage or charged more due to health conditions. Outside of it, in most states, insurers can use medical underwriting to deny coverage or adjust pricing—so the timing of this decision genuinely matters.

Getting Guidance That Fits Your Situation

Comparing Medigap plan letters, premiums across carriers, and how they interact with Part D drug coverage is a lot to sort out on your own, especially with a decision this consequential. BKUHL Insurance works with multiple Medicare Supplement carriers and can walk you through your specific options, timing, and costs so you can make this decision with confidence rather than guesswork.