Medicare has changed over the years from a two-part hospital and doctor program for retirees into a four-part system covering nearly 70 million Americans, including younger adults with disabilities, private plan options, prescription drug coverage, negotiated drug prices, and free preventive screenings. Each major piece was added by separate legislation across six decades, and understanding that sequence is the clearest way to see why today’s program looks the way it does.
1965: The Original Two-Part Program
President Lyndon B. Johnson signed the Social Security Amendments of 1965 on July 30, creating Medicare as a federal health insurance program for people aged 65 and older.1National Archives. Medicare and Medicaid Act (1965) The law built a two-part structure that remains the foundation.
Part A, Hospital Insurance, covers inpatient hospital stays and is funded primarily through payroll taxes that workers and employers pay throughout their careers. Most people who paid Medicare taxes for at least ten years qualify for Part A without a monthly premium.2Medicare.gov. Costs
Part B, Medical Insurance, covers doctor visits, outpatient care, and medical supplies. It is funded by a combination of enrollee premiums and general federal revenue.3Medicare.gov. How is Medicare funded?
The original program was designed for retirees moving onto fixed incomes at a time when private insurers routinely denied or overcharged older applicants. It gave that generation a guaranteed baseline of medical coverage backed by the federal government.
1972: Coverage for People Under 65
The 1972 Social Security Amendments were the biggest expansion of Medicare since its creation. Congress recognized that severe medical expenses weren’t limited to people over 65 and opened the program to two new groups.4Social Security Administration. 1972 Social Security Amendments
The first group was people under 65 who had received Social Security disability benefits for at least 24 consecutive months. That two-year waiting period was intentional: lawmakers wanted to limit coverage to those with lasting impairments rather than short-term conditions.4Social Security Administration. 1972 Social Security Amendments
The second group was people with end-stage renal disease who needed regular dialysis or a kidney transplant. ESRD coverage was available regardless of age but required a connection to Social Security. You had to have worked long enough to be insured under Social Security, already be receiving benefits, or be the spouse or dependent child of someone who met those requirements.5Medicare.gov. End-Stage Renal Disease (ESRD) Dialysis costs were devastating for families in the early 1970s, and Congress treated chronic kidney failure as effectively equivalent to a disability for Medicare purposes.
The 2000 ALS Exception
In 2000, Public Law 106-554 eliminated the 24-month waiting period for people diagnosed with amyotrophic lateral sclerosis. Because ALS progresses rapidly, forcing patients to wait two years for coverage made little medical sense. Under current law, Medicare begins the first month a person with ALS starts receiving disability benefits.6Office of the Law Revision Counsel. 42 USC 426 – Entitlement to Hospital Insurance Benefits
1990: Standardized Medigap Plans
Original Medicare was never designed to cover everything. Deductibles, coinsurance, and coverage gaps left enrollees responsible for potentially large bills, and a private market for “Medigap” supplemental insurance policies emerged to fill those gaps. By the late 1980s, hundreds of different policy designs flooded the market. Comparing them was nearly impossible, and deceptive sales practices targeting seniors were a recurring problem.
Congress addressed this through the Omnibus Budget Reconciliation Act of 1990, which required all Medigap policies sold after July 1992 to conform to one of ten standardized benefit packages labeled Plan A through Plan J. Every carrier selling Medigap coverage had to offer Plan A and could choose to sell any of the remaining packages. Standardization meant that a Plan F from one insurer covered exactly the same benefits as a Plan F from another, making it straightforward to shop by price alone. Later adjustments updated the letter designations, and the most popular plans today are Plan G and Plan N, but the core principle of standardized, comparable packages remains in place.
1997 and 2003: Private Plans Become Medicare Advantage
The Balanced Budget Act of 1997 created a program called Medicare+Choice, which for the first time gave beneficiaries the option to receive their Part A and Part B benefits through private managed care organizations instead of the government-administered system.7Congressional Budget Office. Medicare+Choice Provisions in the Balanced Budget Act of 1997 The idea was to bring private-sector competition and plan variety into a program that had operated as a single fee-for-service payer for three decades.
The Medicare Prescription Drug, Improvement, and Modernization Act of 2003 overhauled this option and renamed it Medicare Advantage, or Part C. The redesign expanded the types of private plans that could participate and gave them more flexibility to bundle additional benefits like dental, vision, and hearing coverage that Original Medicare doesn’t include.8The White House. Fact Sheet – Medicare Prescription Drug, Improvement, and Modernization Act of 2003
The federal government pays each Medicare Advantage insurer a fixed per-enrollee amount, and the insurer takes on responsibility for managing care within that budget. Growth has been enormous. As of 2025, over 35 million people are enrolled in Medicare Advantage, roughly half of all Medicare beneficiaries.9Centers for Medicare & Medicaid Services. Medicare Monthly Enrollment That’s a striking shift for a program originally built around government-administered coverage.
2003: Prescription Drug Coverage Arrives
The same 2003 law that renamed Medicare Advantage also addressed a glaring hole in the program. Medicare had no outpatient prescription drug benefit. For nearly four decades, the program covered drugs administered in a hospital but offered nothing for the medications people filled at a pharmacy. That gap became increasingly painful as modern medicine grew more reliant on pharmaceutical treatments.
The law created Part D, a voluntary prescription drug benefit delivered through private insurance plans. To bridge the gap before full implementation, the government introduced temporary drug discount cards that offered 10 to 25 percent savings on most medications.8The White House. Fact Sheet – Medicare Prescription Drug, Improvement, and Modernization Act of 2003 The full Part D benefit launched in January 2006.
Enrollees choose from competing private plans with different drug formularies, pharmacy networks, and cost structures. Part D was the largest expansion of Medicare benefits since the program’s creation, and it remains the primary way most enrollees manage pharmacy costs.
2010: The Affordable Care Act
The Affordable Care Act brought several targeted changes to Medicare, with the biggest impact on preventive care and prescription drug costs. The law eliminated out-of-pocket costs for a wide range of preventive screenings and wellness visits, removing a financial barrier that had discouraged many enrollees from catching health problems early.10HHS.gov. About the Affordable Care Act (ACA)
Today, Medicare Part B covers dozens of preventive services at no cost to you, including mammograms, colonoscopies, cardiovascular disease screenings, diabetes screenings, annual wellness visits, and vaccinations for flu, pneumonia, COVID-19, and hepatitis B.11Medicare.gov. Preventive and Screening Services The only catch is that you need to see a provider who accepts Medicare assignment.
The ACA also began phasing out the so-called “donut hole” in Part D drug coverage. Under the original Part D design, enrollees paid a share of drug costs up to a certain threshold, then bore the full cost of their medications through a coverage gap before catastrophic coverage kicked in. That gap was a nasty surprise for people with expensive prescriptions. The ACA gradually closed it by shifting more of the cost in the gap to drug manufacturers and the federal government.
2022: The Inflation Reduction Act
The Inflation Reduction Act of 2022 made what may be the most consequential changes to Medicare drug costs since Part D was created. Three provisions stand out.
First, the law gave the federal government authority to negotiate prices directly with drug manufacturers for certain high-cost medications covered under Medicare. This reversed an explicit prohibition written into the 2003 law that created Part D. The first round of negotiations covered ten widely used Part D drugs, including the blood thinners Eliquis and Xarelto, the heart failure drug Entresto, and the diabetes medications Jardiance and Januvia. Those negotiated prices took effect on January 1, 2026.12Centers for Medicare & Medicaid Services. Selected Drugs and Negotiated Prices
Second, the law requires drug manufacturers to pay rebates to Medicare when they raise prices faster than inflation, creating a financial check on runaway price increases for existing drugs.13Centers for Medicare & Medicaid Services. Medicare Inflation Rebate Program Overview
Third, the law capped annual out-of-pocket spending on Part D prescription drugs. The cap started at $2,000 in 2025 and increased to $2,100 in 2026.14Medicare.gov. How much does Medicare drug coverage cost? Before this cap existed, enrollees with very expensive prescriptions could face annual out-of-pocket costs of $10,000 or more. The cap provides a hard ceiling that makes drug spending predictable in a way it never was under the original Part D structure.15U.S. Department of Health and Human Services / ASPE. The Inflation Reduction Act of 2022 – One Year Anniversary Highlights from ASPE Drug Pricing Reports
Where the Program Stands in 2026
Six decades of amendments have left Medicare with a shape the 1965 architects would only partly recognize. The two-part core still exists: Part A carries an inpatient deductible of $1,736 per benefit period in 2026, and the standard Part B premium is $202.90 per month, with higher-income enrollees paying more.16Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles For people who lack the ten years of Medicare-taxed work needed for premium-free Part A, the Part A premium runs up to $565 per month in 2026.2Medicare.gov. Costs
Around that core sit the pieces added later: Part C, which delivers the same A and B benefits through private plans and now enrolls about half of all beneficiaries; Part D, which brought outpatient drug coverage in 2006 and gained a hard out-of-pocket cap in 2025; ten standardized Medigap letter plans for people who stay in Original Medicare; and, for the first time in the program’s history, a set of prices negotiated between the federal government and drug manufacturers. The eligibility door has widened too, from people 65 and older in 1965 to include those on Social Security disability for 24 months, those with end-stage renal disease, and those with ALS from the first month of disability benefits.