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Do I need Medicare if I have insurance through my employer?

It depends on how many people your employer has. With 20 or more you can usually delay Part B. Under 20, Medicare pays first and you need it now.

Updated September 3, 2026 · 4 min read · by Gerino Alejos

Not always. Having insurance through a job at 65 does not mean you can skip Medicare. What matters is which plan pays first, and that depends on how many people your employer has. With 20 or more, you can usually delay. With fewer than 20, you need Part B now. Medicare explains how employer coverage affects your timing on medicare.gov.

Which plan pays first: coordination of benefits

When you have two sources of coverage, one is primary and pays first. The other is secondary and picks up some of what is left. Insurers call this coordination of benefits.

If the plan that is supposed to pay first is not in place, the secondary plan still pays only its secondary share. The difference lands on you.

20 or more employees: your employer plan pays first

Your group plan is primary. Medicare is secondary.

You can delay Part B, the part of Medicare that pays for doctor visits, without a penalty for as long as you are working and covered. Most people still take Part A, the part that pays for hospital stays, because it is premium free, meaning no monthly bill. It can act as secondary coverage on hospital bills at no cost to you.

The exception is a Health Savings Account (HSA). Enrolling in any part of Medicare, even Part A alone, ends your ability to put money in.

Fewer than 20 employees: Medicare pays first

Medicare is primary. Your group plan is secondary.

This is where people get hurt. If you have not enrolled in Part B, your group plan can handle a claim as if Medicare had already paid its 80 percent, then pay only its share of what is left. You owe the piece Medicare would have paid, even though you never had Medicare.

On a $1,000 doctor bill, Medicare would have paid $800. The plan pays only its part of the other $200, and the $800 comes out of your pocket.

How to count employees when it is not obvious

The 20 employee line is counted across the whole employer, not just your location. It generally means 20 or more employees for at least 20 weeks in the current or prior calendar year. Part time employees usually count.

If you work at a small branch of a large company, the large company's count applies. Ask HR to confirm it in writing.

Situations with different rules

• Coverage based on a disability rather than age uses a 100 employee line instead of 20.
• End stage renal disease (kidney failure) has its own timeline. The group plan generally pays first for 30 months.
• Retiree coverage always pays second to Medicare, no matter how big the employer is. If you are on retiree coverage, you need Part B.
• COBRA, the coverage you can keep for a while after leaving a job, also pays second. Do not treat it as employer coverage when deciding whether to delay.

Part D and creditable drug coverage

Separate from all of the above, your employer plan should send you a notice each fall saying whether its drug coverage is creditable. Creditable means at least as good as Part D, the part of Medicare that covers prescriptions. Keep those notices. If the coverage is not creditable, a Part D penalty builds up whether anyone warned you or not.

The rule in one sentence

Twenty or more employees and still working means you can usually delay Part B; fewer than 20, retiree coverage or COBRA means you need it now.

1. Find out the employee count and get it in writing.
2. 20 or more and still working: you can usually delay Part B safely.
3. Under 20, or on retiree coverage or COBRA: you almost certainly need Part B now.
4. Putting money in an HSA: stop at least six months before you enroll in anything.
5. Either way, keep the creditable coverage notice.

For the steps when you do retire, see applying for Medicare after 65. If you want us to look at your employer plan with you, call the office or enter your ZIP code in the form on this page.

Gerino Alejos

Licensed insurance agent · License 3128710 · NPN 18243381

Owner of McAllen Insurance Group, an independent agency on North 10th Street in McAllen. Works with clients across Hidalgo, Cameron and Starr counties on Medicare, Marketplace health, life and auto coverage. Se habla español.