The full-benefit low-income subsidy (LIS) group that is eligible for both Medicare and full Medicaid pays USD 0 for generic drugs and USD 0 for brand drugs in 2024. This is the only LIS category with a double-zero cost-sharing schedule. Full-benefit LIS enrollees without full Medicaid pay USD 4.50 generic and USD 11.20 brand; the 2025 figures are USD 4.90 and USD 12.15.
The four LIS cost-sharing tiers, explained
The Medicare Part D low-income subsidy is not one benefit but four distinct cost-sharing schedules, each tied to an income and asset test. The tiering exists because Congress wanted to link copay relief to the depth of poverty, not just to enrollment in Part D. The Centers for Medicare & Medicaid Services (CMS) publishes the thresholds annually in a memo that plans must apply to every claim.
The four levels are: full LIS plus full Medicaid (the "institutional" or dual-eligible tier), full LIS without Medicaid, partial LIS, and no LIS. The first group receives the 0/0 schedule. The second receives a fixed nominal copay. The third pays a percentage of drug cost. The fourth pays the standard plan cost-sharing. CMS sets the copay amounts each January.
The mechanism that produces the double zero is not a discount inside the Part D plan. It is a subsidy payment. For dual-eligible enrollees, the state Medicaid agency pays the Part D premium and cost-sharing on the beneficiary's behalf. The pharmacy collects nothing from the patient at the counter. Behind the scenes, the plan bills the state and CMS for the amount the patient would otherwise owe. This is why the 0/0 copay appears only where Medicaid is also paying.
A plain-language version: the Part D plan sets a price, and the state Medicaid program picks up the entire tab for this group. The patient's copay is zero because someone else is legally obligated to pay it.
Why the 0/0 schedule exists and where the money comes from
The 0/0 schedule is a consequence of two overlapping federal statutes, not a single program. Part D (the Medicare Modernization Act of 2003) created the LIS to reduce premiums and cost-sharing for low-income enrollees. Medicaid (Title XIX) already covered prescription drugs for its beneficiaries before Part D existed. When Part D launched, Congress required states to keep paying a share of the cost for dual-eligible people so states would not shift their drug costs onto the federal government.
That "clawback" arrangement is why the federal government funds most of the LIS subsidy, while states fund the Medicaid wrap-around that zeroes out the copay. The dual-eligible group therefore has two payers. Full-benefit LIS enrollees who are not on Medicaid have only one payer, the federal LIS trust fund, and that payer does not cover the full cost, hence the nominal copay.
The 2024 nominal copays for the non-Medicaid full-benefit group are USD 4.50 for generics and USD 11.20 for brand drugs. Those amounts are set by statute and indexed. They are not the "0/0" schedule. Any beneficiary who tells you their copay is zero on both generics and brands is, almost by definition, dual-eligible or in an equivalent Medicaid-paid category.
Quantified context: income limits, asset limits, and the gap between tiers
The income thresholds move every year. For 2024, the full-benefit LIS income limit for a single person is roughly 150% of the federal poverty level, with an asset limit near USD 17,000 for an individual and USD 34,000 for a couple (the exact figures are published in the annual CMS memo and the Social Security Administration's LIS materials). The partial-benefit LIS extends to about 200% of poverty, with higher asset limits. Those are the numbers that separate a 0/0 enrollee from a USD 4.50 enrollee.
The financial gap is large. A full-benefit non-Medicaid enrollee with 24 generic fills a year pays about USD 108 in 2024 just in copays, and more if they use brands. A dual-eligible enrollee with the same fills pays USD 0. Over a decade, that difference can exceed USD 1,000 for a heavy user of brand drugs, because the brand copay is USD 11.20 versus zero.
The population is not small. CMS estimates that roughly 9 to 10 million Part D enrollees receive some form of LIS in a given year, and a substantial fraction of those are dual-eligible. The double-zero group is therefore millions of people, not a niche. Yet the category is routinely described incorrectly in consumer materials, which is why the keyword question keeps surfacing.
(Exact counts and thresholds change with each annual update; treat the dollar figures above as 2024 values and verify against the current CMS memo before relying on them.)
Edge cases that break the simple rule
The clean statement "dual-eligible equals 0/0" is true at the pharmacy counter but bends in four situations.
First, some dual-eligible people are in Medicare Advantage plans rather than standalone Part D. The 0/0 LIS schedule still applies to the Part D drug benefit inside the MA plan, but the plan may have its own formulary rules that determine whether a drug is covered at all. A zero copay on a drug the plan does not cover is still no drug.
Second, institutionalized beneficiaries (people in long-term care) and homebound people receiving Medicaid home care are a subset of dual-eligibles with a special 0/0 schedule. The pharmacy billing path differs, but the patient pays nothing. This is a common source of confusion when families compare bills across settings.
Third, people who qualify for full LIS but lose Medicaid mid-year (for example, after an income change) can drop from 0/0 to the nominal copay tier. The transition is not always instantaneous, and the patient may see a copay before the state updates its records. This is the counterintuitive part: eligibility is continuous in law, but the billing system catches up on a lag.
Fourth, some states have their own pharmaceutical assistance programs that zero out or reduce copays for partial-LIS people. Those state programs are separate from the federal 0/0 category and can make a partial-LIS person look like a 0/0 person at the counter. Do not assume a 0/0 receipt proves federal dual-eligible status.
Side-by-side comparison of LIS tiers
| LIS tier | Generic copay (2024) | Brand copay (2024) | Who qualifies (broadly) |
|---|---|---|---|
| Full LIS + full Medicaid | USD 0 | USD 0 | Dual-eligible; income near 150% FPL and low assets |
| Full LIS, no Medicaid | USD 4.50 | USD 11.20 | Income near 150% FPL, low assets, not Medicaid-eligible |
| Partial LIS | Percentage of cost, capped | Percentage of cost, capped | Income up to ~200% FPL, higher asset limit |
| No LIS | Plan standard cost-sharing | Plan standard cost-sharing | Above LIS limits |
The 2025 nominal copays for the non-Medicaid full-benefit tier rise to USD 4.90 and USD 12.15. The 0/0 row does not change because it is a pass-through payment, not a fixed nominal amount. If you are comparing years, hold the 0/0 row constant and expect the other rows to drift upward with indexing.
A plain reading of the table: only the first row is double-zero, and the distinguishing feature is the Medicaid connection, not the income level alone.
Common misconceptions, corrected
Misconception one: "All full-benefit LIS enrollees pay zero." False. Full-benefit LIS without Medicaid pays the nominal copays above. The 0/0 schedule is specific to the Medicaid-linked group.
Misconception two: "Extra Help always means zero copays." Extra Help is the marketing name for the LIS. It reduces copays but does not always eliminate them. The zero is conditional on the Medicaid piece.
Misconception three: "Partial LIS is basically the same as full LIS." No. Partial LIS uses a percentage-based cost-sharing formula with caps, and the out-of-pocket exposure is materially higher. The gap between partial and full is larger than the gap between full and 0/0 for many enrollees.
Misconception four: "The income limit is the only test." Asset limits also apply, and they differ by tier and by household size. A person can be under the income limit and still fail the asset test, which changes the tier.
Red-flag warnings to keep in mind:
A pharmacy that quotes a nonzero copay to a known dual-eligible person may have a stale eligibility file, not a wrong rule. A "zero copay" receipt does not by itself prove federal dual-eligible status; state assistance programs can mimic it. Losing Medicaid, even briefly, can move a person off the 0/0 schedule, and reinstatement is not always same-day. Plan formulary exclusions apply at every tier, including 0/0. Nominal copay amounts and income limits change annually; a figure from an old article may be wrong.
Practical actions: confirming your tier and protecting the zero
The first step is to confirm which tier you are in, not to assume it from a copay. Call 1-800-MEDICARE or your State Health Insurance Assistance Program (SHIP) and ask specifically whether you are coded as full LIS with Medicaid, full LIS without Medicaid, or partial LIS. The SHIP counselors are federally funded and free.
The second step is to verify the Medicaid linkage. If you believe you are dual-eligible but the pharmacy charges a copay, ask the plan's member services to check the eligibility file date. A common fix is a state Medicaid update that has not propagated to the Part D plan. Request a retroactive adjustment if the lag caused an overcharge.
The third step is to re-check thresholds each fall, before the January copay reset. The income and asset limits and the nominal copay amounts are published annually. A person near the 150% FPL line can cross it with a small raise and should plan for the tier change rather than be surprised by it.
The fourth step, for partial-LIS enrollees, is to ask whether any state pharmaceutical assistance program applies. Some states supplement the federal partial LIS. That is not the federal 0/0 category, but it can reduce the gap.
The final step is documentation. Keep the plan's written confirmation of your tier and the date. If a pharmacy or plan later disputes the copay, the written record resolves it faster than a phone call.
Limitations and what this article cannot tell you
This article explains the structure of the LIS cost-sharing tiers and why the 0/0 schedule attaches to the dual-eligible group. It does not tell you your own tier, because that depends on your income, assets, household size, and Medicaid status, which only CMS, your state Medicaid agency, or a SHIP counselor can determine.
The dollar figures cited are 2024 values with 2025 nominal copays noted where published; they are not guaranteed current for any later year. Exact income and asset thresholds are updated annually and should be verified against the current CMS memo or SSA materials. No article can substitute for an official eligibility determination.
This is general educational information about Medicare Part D and Medicaid cost-sharing, not a diagnosis, treatment plan, legal opinion, or financial or insurance recommendation. It does not promise any outcome or savings. For your own eligibility, enrollment, or billing dispute, consult a qualified local benefits counselor, SHIP program, or Medicaid office.