Medicare is secondary when you have other insurance that should pay first

Medicare becomes your secondary insurance when you are covered by another health plan — usually through your current job, your spouse's job, or TRICARE (military coverage). Secondary means Medicare pays only after that other plan has paid its share. The other plan is called primary insurance and must process your claim first.

Which plan is primary depends on your age and work status, not on which one you signed up for first. Medicare has specific rules about this. If you are under 65 and covered by an employer plan through work, that employer plan is primary even if you enrolled in Medicare. If you are 65 or older and still working, your employer plan is usually primary if your employer has 20 or more employees. If your employer has fewer than 20 employees, Medicare is primary.

The order matters because it affects what you pay out of pocket. When Medicare is secondary, you do not pay Medicare's deductible or coinsurance — you pay only what your primary plan requires. But if your primary plan does not cover something that Medicare would cover, Medicare may still pay its share.

Key Takeaways

  • Medicare is secondary when you have active employer coverage, TRICARE, or certain other health plans, and those plans must process your claim before Medicare does.
  • If you are under 65 with employer coverage, that coverage is primary even if you enrolled in Medicare early.
  • If you are 65 or older and your employer has 20 or more employees, your employer plan is primary; if fewer than 20, Medicare is primary.
  • When Medicare is secondary, you typically pay only what your primary plan requires, not Medicare's separate deductible.
  • You must tell both your doctor's office and your primary insurance that you have Medicare, so claims route correctly.

How the primary-secondary order works in practice

When you see a doctor or get treatment, the provider sends the bill to your primary insurance first. That plan reviews the charge, decides what it will pay, and sends you an explanation of benefits (EOB). Then the provider or the insurance company forwards the remaining balance to Medicare as your secondary payer.

Medicare then looks at what is left unpaid and decides whether to cover it under its rules. Medicare will not pay more than it would have paid if it were primary. For example, if Medicare's allowable amount for a service is $100 and your primary plan already paid $80, Medicare will not pay the remaining $20 if that would push the total above $100. You would owe the $20.

This process takes longer than having Medicare as primary because the claim has to move through two systems. Expect the full payment cycle to take four to eight weeks instead of two to three weeks. During that time, the provider may send you a bill. You can ask them to wait for the secondary payment to process before you pay.

When you work and have both employer coverage and Medicare

If you are working and your employer offers health insurance, you can enroll in both your employer plan and Medicare at the same time. You do not have to choose one or the other. Many people do this because employer plans and Medicare cover different things — your employer plan might have a lower deductible for office visits, while Medicare covers more preventive services without a copay.

The key is telling your employer's benefits office that you have Medicare. Give them a copy of your Medicare card. They need this information to coordinate benefits correctly and to know that Medicare exists as a backup. If you do not tell them, claims may not route properly and you could end up paying more than you should.

If your employer has 20 or more employees, federal law requires your employer plan to be primary. Your employer cannot make Medicare primary just because you are old enough to have it. If your employer has fewer than 20 employees, Medicare becomes primary automatically, and your employer plan is secondary.

TRICARE and other government coverage with Medicare

If you are a military retiree or dependent with TRICARE coverage, TRICARE is your primary insurance and Medicare is secondary. This applies even if you are under 65 and enrolled in Medicare early. TRICARE processes the claim first, and then Medicare handles what TRICARE does not cover.

The same rule applies if you have Veterans Affairs (VA) coverage. The VA is primary for services the VA covers, and Medicare is secondary. If you use a non-VA provider, you would typically submit to Medicare first since the VA is not involved in that claim.

Other government programs like Federal Employee Health Benefits (FEHB) are also primary over Medicare. If you are a federal employee or retiree with FEHB, that plan pays first.

What happens when you turn 65 and stop working

When you retire and your employer coverage ends, Medicare automatically becomes your primary insurance. You do not have to do anything — the change happens on the date your employer coverage stops. After that date, send claims to Medicare first, not to your former employer's plan.

If you retire before 65, you may keep your employer coverage as primary and Medicare as secondary until you turn 65. Some retirees do this because their employer plan has lower out-of-pocket costs. When you turn 65, your employer plan remains primary only if you are still employed or if your employer continues to offer retiree coverage. If your employer coverage ends, Medicare becomes primary.

Check with your employer's benefits office about what happens to your coverage when you retire. Some employers offer retiree health plans that stay primary even after you leave the company. Others end coverage at retirement. Knowing this ahead of time prevents billing problems later.

Telling your providers which insurance is primary

When you schedule an appointment, tell the office staff that you have both Medicare and another insurance plan. Give them your primary insurance card first, then your Medicare card. Ask them to bill your primary plan first. Write both insurance names and member IDs on any forms they give you.

If the office staff seem confused about the order, explain it clearly: "My employer plan is primary. Please send the claim there first. After they process it, send the remaining balance to Medicare." Many offices handle secondary claims regularly, but some smaller practices may not, so being specific helps.

If a provider bills Medicare first by mistake, you can ask them to resubmit the claim to your primary plan. This does not happen often, but it is worth checking your explanation of benefits to make sure the claim went to the right plan first. If it did not, call the provider's billing department and ask them to correct it.

Costs when Medicare is secondary

Your out-of-pocket costs depend on what your primary plan requires. If your primary plan has a $500 deductible and you have not met it, you pay the $500 to that plan first. Medicare's deductible does not explore because Medicare is not the first payer. Once your primary plan has paid its share, Medicare may cover additional costs, but you would not pay Medicare's separate deductible.

Coinsurance works the same way. If your primary plan requires you to pay 20 percent coinsurance, you pay that to the primary plan. Medicare may cover some of what is left, depending on its rules, but you do not pay Medicare's coinsurance on top of your primary plan's coinsurance.

In some cases, having secondary Medicare coverage actually saves you money. If your primary plan has high out-of-pocket limits or does not cover a service, Medicare may cover it. This is why many people keep both plans even when it means paying two premiums.

Frequently Asked Questions

Do I have to pay Medicare premiums if Medicare is secondary?

Yes. You pay your Medicare Part B and Part D premiums regardless of whether Medicare is primary or secondary. You also pay your primary insurance premiums. Having Medicare as secondary does not reduce your Medicare costs, but it may reduce your overall out-of-pocket costs for medical care because you have two plans covering different portions of the bill.

What if my primary plan and Medicare disagree about what to cover?

Medicare will not pay if your primary plan says the service is not covered. Medicare follows the primary plan's decision. If you think the denial is wrong, you would appeal to your primary plan first. If your primary plan overturns the denial, you can then ask Medicare to reconsider.

Can I switch which insurance is primary?

No. The rules about which plan is primary are set by federal law, not by your choice. If you are working and your employer has 20 or more employees, your employer plan must be primary — you cannot make Medicare primary instead. If you want Medicare to be primary, you would need to stop working or move to an employer with fewer than 20 employees.

What if I did not tell my employer I have Medicare?

Tell them now. Contact your benefits office and provide a copy of your Medicare card. They will update their records and coordinate benefits going forward. Claims submitted after they receive this information should route correctly. For past claims that may have routed wrong, contact the provider's billing office and ask them to resubmit to your primary plan.

Does Medicare secondary coverage work the same way at all doctors?

Yes, the coordination rules are the same everywhere. However, some providers are faster at submitting secondary claims than others. If a provider seems unfamiliar with secondary billing, ask to speak with their billing supervisor and explain the process. Larger medical centers usually handle this routinely.