Medicare is primary when you have both programs
When you are enrolled in both Medicare and Medicaid, Medicare pays first on your medical bills. Medicaid then pays what Medicare does not cover — copayments, coinsurance, and deductibles. This order is set by federal law and does not change based on your state or your specific situation.
The reason Medicare goes first is straightforward: it is the federal program you paid into through payroll taxes during your working years. Medicaid is a state-federal program designed to cover people with low income. Because you have already contributed to Medicare, it takes the primary role.
This matters because it changes what you owe out of pocket. Medicare alone leaves you responsible for deductibles and coinsurance. Medicaid filling the gap means you may owe nothing at all at the point of care — or only a small copay that varies by state.
Key Takeaways
- Medicare always pays first; Medicaid pays second and covers what Medicare leaves unpaid.
- You must be enrolled in both programs for this order to explore — having Medicaid alone or Medicare alone works differently.
- Your state Medicaid program sets the exact copayments and coinsurance amounts Medicaid will cover after Medicare pays.
- Providers must bill Medicare first, then send the remaining bill to Medicaid; you should never have to handle this yourself.
- If you have other insurance (employer coverage, Veterans benefits, or a Medigap policy), the order becomes more complex and depends on the type of coverage.
How the two programs work together in practice
When you see a doctor or go to the hospital, the provider's billing office submits the claim to Medicare first. Medicare processes it, applies your deductible if you have not met it yet, and pays its share — usually 80 percent of approved charges for most services.
The provider then automatically sends the remaining balance to Medicaid. Medicaid reviews what Medicare paid and what you still owe. In most states, Medicaid covers your Medicare deductible, copayments, and coinsurance in full. Some states cover most but not all of these costs; a few have small copayments of their own.
You should receive an explanation of benefits from Medicare first, then a separate one from Medicaid. Keep both — they show what each program paid and what you owe. In most cases, you owe nothing if both programs have processed the claim.
What happens if a provider bills Medicaid first by mistake
Occasionally a provider's billing office makes an error and sends the claim to Medicaid before Medicare. When this happens, Medicaid is required by law to deny the claim and tell the provider to bill Medicare instead. The provider must then resubmit to Medicare.
This delay can take weeks. If you receive a bill during this time, do not pay it. Contact the provider's billing office, give them your Medicare number, and ask them to resubmit the claim to Medicare. You can also contact your state Medicaid office if the provider refuses to correct the error.
Some providers, especially small practices or rural clinics, may not be familiar with the Medicare-first rule. If you encounter this repeatedly with the same provider, call your state Medicaid office and report it — they track these patterns and can send guidance to providers.
When you have Medicare, Medicaid, and other insurance
The order becomes more complicated if you also have employer coverage, TRICARE (Veterans), or a Medigap policy. The general rule is: Medicare is still primary, but the order of the other programs depends on what type they are and when you enrolled.
If you have employer coverage and are still working, your employer plan may actually be primary to Medicare in some cases — this is called the working aged exception. Your employer's benefits office can tell you the order. If you are retired, Medicare is primary and your employer plan is secondary.
If you have TRICARE, Medicare is primary and TRICARE is secondary. If you have a Medigap policy, it is always secondary to Medicare and pays after Medicare has paid. Medicaid still comes last in all these scenarios.
Your responsibility when claims are processed
You should not have to contact either program or the provider to make sure claims are processed in the right order — that is the provider's job. However, you do need to make sure both programs know about each other.
When you first enroll in Medicaid, tell your Medicare account that you now have Medicaid coverage. You can do this by calling Social Security at 1-800-772-1213 or by visiting your local Social Security office. This ensures Medicare's records are correct and prevents billing errors.
Similarly, when you enroll in Medicare, your state Medicaid office should be notified automatically in most states. Check your Medicaid notice to confirm they have your Medicare number. If they do not, contact your state Medicaid office and provide it.
What to do if you receive a bill you think is wrong
If you receive a bill after both Medicare and Medicaid have processed a claim, the bill is usually a mistake. Do not ignore it, but do not pay it when ready either.
First, gather your explanation of benefits from both Medicare and Medicaid. Compare what each one says they paid and what you owe. If the bill matches what you owe according to those documents, you may owe a small copayment — check your state Medicaid program's copayment rules for that type of service.
If the bill does not match, contact the provider's billing office first. Give them your Medicare and Medicaid numbers and ask them to verify the claim was submitted to both programs. If they cannot resolve it, contact your state Medicaid office and ask them to investigate.
State differences in what Medicaid covers after Medicare
While Medicare is primary in every state, what Medicaid covers after Medicare varies. Most states cover your full Medicare deductible, copayments, and coinsurance. A few states cover most but not all of these costs.
Some states also cover services that Medicare does not cover at all — such as dental, vision, or hearing aids. These are covered by Medicaid alone, not as a secondary payment. Your state Medicaid program's website lists what it covers; you can also call your state Medicaid office to ask about a specific service.
If you move to a different state, your Medicaid coverage may change. Contact your new state's Medicaid office within 30 days of moving to update your enrollment and learn what your new coverage includes.
Frequently Asked Questions
What if I have Medicare but not Medicaid yet?
Medicare will be your only coverage and you will owe the full deductible, copayments, and coinsurance. If you have low income, you may be able to enroll in Medicaid. Contact your state Medicaid office or call 211 to learn about income limits and how to enroll in your state.
Can I choose to have Medicaid pay first instead of Medicare?
No. Federal law requires Medicare to be primary when you have both programs. This order cannot be changed by your choice or by your provider's preference. The law exists to protect the Medicare trust fund.
Do I need to tell my doctor I have both Medicare and Medicaid?
Yes. Give your doctor's office both your Medicare card and your Medicaid card at every visit. This ensures the billing office has the correct information and can submit claims in the right order. If you only give them one card, claims may be delayed or sent to the wrong program.
What happens to my Medicaid if I turn 65 and enroll in Medicare?
You can keep both programs. You will automatically be enrolled in Medicare Part A and Part B at 65 if you are already receiving Social Security. Your Medicaid coverage continues, and the two programs work together as described above. Contact your state Medicaid office to confirm your enrollment continues.
If Medicare denies a claim, does Medicaid have to pay it?
Not automatically. Medicaid reviews Medicare's decision. If Medicare denied the claim because the service is not covered, Medicaid will usually deny it too. If Medicare denied it for another reason — such as a coding error — Medicaid may pay it. Contact your state Medicaid office if you believe a denial was wrong.