Medicaid is almost always secondary insurance. Under federal law, Medicaid is designated the “payer of last resort,” meaning every other source of coverage must pay its share of a medical claim before Medicaid contributes anything. If you have private insurance through an employer, Medicare, workers’ compensation, or auto insurance, those plans pay first. Medicaid picks up what’s left.
Why Medicaid Pays Last
The payer-of-last-resort rule isn’t a guideline or a state-by-state policy. It’s federal law. If another insurer or program has the responsibility to pay for medical costs incurred by a Medicaid-eligible individual, that entity is required to pay all or part of the cost before Medicaid makes any payment. This applies to every type of third-party coverage: employer health plans, auto liability policies, workers’ compensation, lawsuit settlements, and other government programs.
Congress reinforced this rule through the Deficit Reduction Act, which expanded states’ ability to identify other insurers that should be paying first. The law requires private health insurers to share coverage and eligibility data with states, honor the state’s right to recover payments, and avoid denying Medicaid claims on procedural technicalities. It also prohibits insurers from discriminating against someone simply because they’re enrolled in Medicaid.
Medicaid With Private Insurance
If you have both Medicaid and a private health plan, your private plan is always primary. When you visit a doctor or fill a prescription, the provider bills your private insurer first. After that plan pays its portion, Medicaid may cover some or all of the remaining balance, including copays, deductibles, or coinsurance your primary plan leaves behind.
In practice, this means you should always present both insurance cards at a medical visit. The provider’s billing office needs to submit the claim to your private insurer first, wait for that payment or denial, and then bill Medicaid for the remainder. If a provider bills Medicaid first by mistake, the state Medicaid agency can recover that payment later.
Medicaid With Medicare (Dual Eligibility)
About 12 million Americans are enrolled in both Medicare and Medicaid, a group known as “dual eligibles.” For these individuals, Medicare is the primary payer for acute care, hospital stays, and post-acute services like skilled nursing or home health. Medicaid then wraps around Medicare in two important ways: it helps cover Medicare premiums and cost sharing, and it pays for services Medicare doesn’t cover at all, most notably long-term care.
How much Medicaid pays toward your Medicare copays and deductibles depends on your state. States with “full payment” policies cover the entire Medicare cost-sharing amount. States with “lesser of” policies compare the Medicare cost-sharing amount to the gap between what Medicare paid and what the state’s own Medicaid rate would have been. If the Medicaid rate is lower than the Medicare payment, the state pays nothing toward cost sharing, and you cannot be billed for the difference. A few states take a third approach, paying a set percentage of Medicare cost sharing rather than the full amount or the lesser-of calculation.
Liability Claims and Accidents
The same payer-of-last-resort rule applies when a third party is legally responsible for your medical costs. If you’re injured in a car accident and the other driver’s auto insurance covers your medical bills, that insurance pays before Medicaid. The same goes for workers’ compensation injuries or any situation where you receive a legal settlement or judgment that includes medical expenses.
If Medicaid does pay for your care while a liability claim is pending, the state has the right to recover those costs from whatever settlement or insurance payment you eventually receive. States actively pursue these recoveries, and agreeing to let Medicaid recover costs from third parties is a condition of enrollment.
Are There Exceptions?
The situations where Medicaid functions as a primary payer are narrow. If you have no other insurance at all, Medicaid is your only coverage and pays as the sole payer (not technically “primary” in the coordination-of-benefits sense, since there’s no other plan in the picture). It simply covers your care directly.
One notable edge case involves the Indian Health Service. IHS is not an insurance program. It provides services directly at its own facilities, funded by federal appropriations rather than by acting as a payer on claims. For American Indian and Alaska Native individuals who are also enrolled in Medicaid, Medicaid serves as a critical revenue source for IHS facilities. During the 34-day government shutdown in 2019, Medicaid collections became the primary or only source of revenue for many Indian health providers when federal IHS funding was interrupted. But this describes how facilities get paid, not a change in the coordination-of-benefits rules for patients with other coverage.
What This Means at the Doctor’s Office
If you carry Medicaid alongside any other insurance, always give both cards to your provider. Your other coverage pays first, and Medicaid covers the gap. You should rarely owe anything out of pocket for covered services, since Medicaid typically picks up remaining cost sharing. If a provider tells you they can’t bill Medicaid as secondary, that’s a billing office issue, not a coverage issue. The federal rule is clear, and providers are expected to follow the correct billing order.
If your other coverage denies a claim, Medicaid can then step in as payer, but only after the denial. The key principle is straightforward: Medicaid waits for every other responsible party to act first, then fills in whatever remains.