Medicare Advantage vs Original Medicare: What Each Costs for Procedures

Original Medicare is the traditional program: Part A covers hospital care, Part B covers physician and outpatient services, and you can see any provider in the country who accepts Medicare, which the large majority of physicians and essentially all hospitals do. There is no network, and referrals are not required. Drug coverage requires a separate Part D plan.

Medicare Advantage, also called Part C, replaces that arrangement with a private plan that must cover everything Original Medicare covers and usually bundles drug coverage and extras such as dental or vision allowances. In exchange, the plan manages care the way commercial insurance does: provider networks, copay schedules, and prior authorization requirements. Many Advantage plans charge low or zero premiums beyond the Part B premium everyone pays, which is a large part of their appeal.

Under Part B, after a modest annual deductible, you generally pay 20 percent coinsurance of the Medicare-approved amount for physician and outpatient services. The approved amounts are the fee schedule rates this site is built on, so you can look up a procedure and estimate the 20 percent directly. For inexpensive services the coinsurance is trivial. For major outpatient procedures, chemotherapy, dialysis, or a long run of imaging and specialist care, 20 percent of everything adds up fast.

The critical structural fact: Original Medicare has no out-of-pocket maximum. There is no annual ceiling at which the program starts paying 100 percent. A serious illness can generate unlimited 20 percent exposure, plus hospital deductibles and coinsurance under Part A for long stays. This is not a flaw people discover in good years; it is the reason supplemental coverage exists, and why going truly bare on Original Medicare, with no Medigap, no employer retiree coverage, and no Medicaid, is a genuine financial risk.

Medigap policies, also called Medicare Supplement plans, are private policies that pay some or most of Original Medicare's cost sharing, including the Part B coinsurance. The plans are standardized by letter, so a given plan letter has the same benefits from any insurer, and with a comprehensive plan your out-of-pocket exposure for Medicare-covered services becomes small and predictable. You keep Original Medicare's see-any-provider freedom; Medigap simply pays the patient share behind it.

The cost is a real monthly premium on top of Part B, and premiums vary by plan letter, insurer, age, and location. The catch that dominates long-term planning: your strongest purchase right is the open enrollment window around when you first enroll in Part B, when insurers must sell to you regardless of health. Outside protected windows, Medigap insurers in most states can medically underwrite: they can decline you or charge more based on health history. In practice this means the choice between Advantage and Original-plus-Medigap can be hard to reverse later, because the Medigap door may not reopen once your health has changed. Some states have more generous rules; check yours before assuming either way.

Advantage plans replace the 20 percent structure with their own cost sharing: flat copays for many services, coinsurance for others, varying plan by plan. For routine care the copays are often modest and predictable. For major procedures, the plan's schedule controls, and cost sharing for things like outpatient surgery, hospital stays, or chemotherapy can still be substantial until you reach the cap.

The cap is the headline advantage: every Medicare Advantage plan must have an annual out-of-pocket maximum for covered in-network services, a protection Original Medicare simply lacks. Federal rules set the highest allowable limit and plans often set theirs lower. The trade is control. Advantage plans use networks, and out-of-network care may cost more or not be covered at all depending on whether the plan is an HMO or PPO. A procedure under Advantage is a managed transaction: the right surgeon must be in network, the facility must be in network, and the plan must approve it.

Original Medicare requires prior authorization for very little; for most procedures, if your physician says it is medically necessary and Medicare covers the service, it proceeds. Medicare Advantage plans use prior authorization extensively for imaging, surgeries, hospital admissions, and post-acute care such as skilled nursing and rehabilitation stays. Most requests are ultimately approved, and appeal rights exist with strong overturn rates, but the friction is real: delays before treatment, denials to fight during illness, and pressure to shorten rehabilitation stays.

Network churn matters too. Advantage networks change year to year, and a plan that includes your surgeon and hospital today may not next January. Plan details, premiums, copays, drug formularies, and networks reset annually, so Advantage enrollees should genuinely re-shop every fall during open enrollment rather than letting the plan roll over. Beneficiaries with a serious diagnosis often discover the difference at the worst time: under Original Medicare they could take the diagnosis to any center of excellence in the country; under an Advantage HMO, the question becomes what the network contains and what the plan will authorize.

Take a significant outpatient procedure. Under Original Medicare alone: look up the approved amounts, and expect roughly 20 percent of the physician and outpatient facility amounts after the Part B deductible, with no ceiling if complications multiply the services. Under Original Medicare with comprehensive Medigap: the Medigap plan pays most or all of that share; your cost is mainly the premiums you have been paying all along. Under Medicare Advantage: the plan's copay or coinsurance schedule applies, prior authorization likely gates the procedure, the surgeon and facility must be in network, and your worst case for the year is the plan's out-of-pocket maximum.

The pattern generalizes. Original plus Medigap converts procedure costs into fixed premiums: expensive every month, calm in a crisis. Advantage minimizes monthly cost and caps catastrophe, but concentrates cost and friction in the sick years, when copays accumulate toward the cap and every step needs approval. Healthy-year math flatters Advantage; sick-year math often favors Original plus Medigap. Since nobody schedules their sick years, the honest comparison is premiums plus realistic worst case under each, not premiums alone. And because Medigap underwriting can lock the door back, treat the initial choice as semi-permanent rather than freely reversible.