Original Medicare is a fee-for-service model health insurance program, and consists of two parts: Part A and Part B.
Medicare Part A provides coverage when someone is an in-patient in a hospital or skilled nursing facility. Medicare Part B covers all other Medicare services that Part A does not cover, such as doctor's visits, outpatient services, x-rays, labs, physical therapy, and medications administered in a medical facility.
Medicare Parts A and B together pay around 80% of someone's health care costs after they pay a once-a-year Medicare Part B deductible, which is $257 in 2025. Preventative services, such as a colonoscopy or a mammogram, are not subject to the deductible, nor are services under Part A.
A Medicare beneficiary may add a Plan G Medicare Supplement to cover the remaining 20% of health care costs not covered by Parts A and B. When someone has Medicare Parts A and B along with a Plan G Medicare Supplement, they can receive care from any doctor that accepts Original Medicare, as 99% of doctors and many hospitals do.
Importantly, Original Medicare has the most generous coverage guidelines of any type of health insurance. This means that someone with Original Medicare combined with a Plan G Supplement has the best chance for the best health outcome possible should they have serious health issues.
On the other hand, Medicare Advantage is a private, for-profit alternative or replacement for Original Medicare in which a Medicare Beneficiary withdraws from having Medicare Parts A and B as their primary coverage and instead consents to having their health care managed by a third-party that makes health care decisions largely based on costs. The primary goal of a Medicare Advantage organization is to spend as little as possible on one's health care because the less the spend, the more they keep as profit.
With a Medicare Advantage plan, the Medicare beneficiary can only receive care from a limited group of doctors, hospitals, and skilled nursing facilities, and, unlike Original Medicare, often must receive a referral to see a specialist.
While someone with Original Medicare combined with a Medicare Supplement has minimal out-of-pocket costs other than their monthly premiums, someone who enrolls in Medicare Advantage pays a series of co-pays based on the amount and type of care they receive, which can add thousands of dollars in unexpected costs throughout the year.
Medicare beneficiaries who leave Original Medicare for Medicare Advantage can only return to Original Medicare at certain times and are often unable to return to Original Medicare if they have have health issues and cannot pass underwriting.
Most Medicare Advantage plans include Medicare Part D drug coverage, and some include extra benefits, such as limited dental, vision, and hearing to entice someone to enroll in their plan.
