Medicare and Employer Insurance: How They Work Together and When to Enroll
If you're turning 65 and still working, you may be able to keep your employer insurance alongside Medicare—or choose one over the other. Here's how to decide.
If you're turning 65 and still working, you may be able to keep your employer insurance alongside Medicare—or choose one over the other. Here's how to decide.
Turning 65 while still working raises important questions about health insurance. Can you have both Medicare and employer coverage? Do you need to sign up for Medicare right away? Will keeping both cost you more—or save you money?
The answers depend on several factors: your employer's size, whether your coverage is through your own job or your spouse's, how your employer plan compares to Medicare, and whether you have a Health Savings Account (HSA).
At Health Plans of NC, we help people navigate these decisions every day. This guide explains how Medicare works with employer insurance, when you must enroll, and how to decide what's best for your situation.
Yes. You can have Medicare and employer health insurance at the same time. When you have both, they coordinate benefits—one pays first (primary), and the other pays second (secondary) for any remaining costs.
This coordination of benefits can provide more comprehensive coverage and lower out-of-pocket costs than having a single insurance plan. However, you'll also pay premiums for both plans.
The key question isn't whether you can have both—it's whether it makes financial sense for your situation.
When you have multiple insurance plans, the coordination of benefits rules determine which plan pays first (primary) and which pays second (secondary). The primary payer covers costs up to its limits, then the secondary payer covers some or all of the remaining balance.
The rule depends on employer size:
Employers with 20+ employees: Your employer insurance pays first (primary), Medicare pays second (secondary). This applies to coverage through your own job or your spouse's job.
Employers with fewer than 20 employees: Medicare pays first (primary), your employer insurance pays second (secondary). You must enroll in Medicare Parts A and B when you become eligible, or your employer plan may not pay its share.
Important: If you're covered through a spouse's employer, the same rules apply based on their employer's size. If you're disabled (under 65) and covered by an employer plan, the employer size threshold is 100 employees, not 20.
If you or your spouse works for an employer with 20 or more employees and has health coverage through that job, you have options:
Option 1: Keep employer coverage and delay Medicare Part B
You can continue using your employer insurance as your primary coverage and delay enrolling in Medicare Part B (and Part D) without penalty—as long as you have creditable coverage through current employment.
Most people in this situation still sign up for Medicare Part A when they turn 65 because it's premium-free (if you or your spouse paid Medicare taxes for at least 10 years). Part A provides additional coverage for hospital stays and can fill gaps in your employer plan.
Option 2: Keep employer coverage AND enroll in Medicare Part B
You can have both employer insurance and full Medicare coverage. Your employer plan pays first, Medicare pays second. This provides comprehensive coverage but means paying premiums for both plans (the Part B premium is $202.90/month in 2026).
Option 3: Drop employer coverage and switch to Medicare
You can leave your employer plan and make Medicare your primary insurance. You'll need Parts A and B, plus a Medicare Part D prescription drug plan. Most people also add either a Medigap (Medicare Supplement) plan or choose Medicare Advantage to reduce out-of-pocket costs.
Which option is best? Compare your employer plan's premiums (including any payroll deductions), deductibles, copays, and coverage to what you'd pay with Medicare plus supplemental coverage. Sometimes Medicare with Medigap is cheaper than employer coverage—especially if your employer doesn't contribute much to your premiums.
If you or your spouse works for an employer with fewer than 20 employees, the rules are different—and important to get right.
Medicare becomes your primary insurance. With a small employer, Medicare pays first, and your employer coverage pays second. This means you must enroll in both Medicare Part A and Part B when you first become eligible at age 65.
What happens if you don't enroll: Your employer plan may refuse to pay benefits (since Medicare should be paying first), and you could face late enrollment penalties when you do sign up for Medicare later.
You can keep your employer coverage as secondary insurance to help cover costs that Medicare doesn't fully pay. Or you can drop the employer plan and rely on Medicare with a Medigap or Medicare Advantage plan instead.
COBRA Coverage
COBRA does not count as coverage from "current employment." If you have COBRA and become eligible for Medicare, Medicare is primary, and COBRA is secondary. You must enroll in Part A and Part B during your Initial Enrollment Period to avoid penalties. If you're already on COBRA when you turn 65, your COBRA coverage typically ends when your Medicare begins.
Important: If you retire after 65 and elect COBRA, you must sign up for Medicare Part B within 8 months—even if your COBRA continues longer. Failure to do so can result in permanent late enrollment penalties and gaps in coverage.
Retiree Health Coverage
Retiree coverage from a former employer is not the same as coverage from current employment. Medicare pays first, and retiree coverage pays second. You should enroll in Medicare Parts A and B during your Initial Enrollment Period. Your retiree plan may require you to have Medicare to receive benefits.
VA Benefits
If you have VA health benefits, the coordination of benefits rules don't apply in the traditional sense. VA facilities don't bill Medicare, so you can only use VA benefits at VA-affiliated facilities. Many veterans enroll in Medicare to have coverage outside the VA system.
Federal Employee Health Benefits (FEHB)
If you're an active federal employee, FEHB is primary, and Medicare is secondary. If you're a retired federal employee (annuitant), Medicare is primary, and FEHB is secondary. You must enroll in Medicare to get the full benefit of your FEHB coverage in retirement.
Once you enroll in any part of Medicare, you can no longer contribute to an HSA. This includes Part A, Part B, or Part D. You can still use funds already in your HSA for qualified medical expenses—you just can't add new money.
The 6-Month Lookback Rule (Critical)
If you delay Medicare enrollment past age 65 and later sign up, Medicare Part A coverage is retroactive by up to 6 months (but not earlier than your 65th birthday). Any HSA contributions you made during that retroactive period become "excess contributions" and are subject to a 6% IRS penalty.
Example: You turn 65 in January 2025 but continue working and don't enroll in Medicare. In July 2025, you retire and apply for Medicare. Your Part A coverage will be retroactive to January 2025. Any HSA contributions you made from January through June are excess contributions.
How to avoid this problem:
• Stop HSA contributions at least 6 months before you plan to apply for Medicare
• If you're turning 65 in January, stop contributions by July of the prior year if you plan to enroll in Medicare at 65
• If you accidentally over-contribute, work with your HSA administrator to remove excess contributions before your tax filing deadline
Can my spouse contribute? If your spouse is not enrolled in Medicare and has their own HSA, they can continue contributing to their HSA—even if you've enrolled in Medicare.
Using HSA funds after enrolling in Medicare: You can use existing HSA funds tax-free to pay for Medicare premiums (Parts B, D, and Medicare Advantage), deductibles, copays, and other qualified medical expenses.
If you delayed Medicare enrollment because you had employer coverage through your current employment (yours or your spouse's), you get a Special Enrollment Period (SEP) when that coverage ends.
8-Month SEP: You have 8 months to sign up for Medicare Part B (and Part D) after your employer coverage ends or your employment ends—whichever happens first. There's no late enrollment penalty if you sign up during this period.
Don't wait: While you have 8 months, it's best to enroll before your employer coverage ends to avoid a coverage gap. Your Part B coverage can start as early as the first day of the month you enroll.
What you'll need: When you enroll, you'll need to provide proof of your prior coverage using Form CMS-L564 (completed by your employer) and Form CMS-40B (your enrollment request).
There's no one-size-fits-all answer. Here's how to evaluate your options:
Compare costs:
• What do you pay monthly for employer coverage (premiums deducted from payroll)?
• What's your employer plan's deductible and out-of-pocket maximum?
• How much would you pay for Medicare Part B ($202.90/month in 2026), Part D, and a Medigap or Medicare Advantage plan?
• Don't forget to factor in any employer contribution—if your employer pays most of your premium, keeping that coverage may be cheaper
Compare coverage:
• Does your employer plan cover your doctors and hospitals?
• How does prescription drug coverage compare?
• Does Medicare or your employer plan have better coverage for services you use frequently?
Consider your situation:
• Do you have an HSA? If so, factor in the contribution rules discussed above
• Are you planning to retire soon? If you'll lose employer coverage within a year or two, it may make sense to transition to Medicare now
• Is your spouse covered under your employer plan? They may be able to continue coverage after you switch to Medicare, or they may need to find their own coverage
Deciding between employer coverage and Medicare involves comparing premiums, deductibles, copays, prescription drug costs, and coverage details. It can get complicated quickly.
At Health Plans of NC, our Medicare agents specialize in helping North Carolina residents navigate these decisions. We can help you:
• Compare the total cost of your employer plan vs. Medicare with supplemental coverage
• Understand whether you must enroll in Medicare or can delay
• Navigate HSA rules and avoid IRS penalties
• Enroll in Medicare, Medigap, or Medicare Advantage when you're ready
Contact us at 1-800-797-0327 for a free consultation. We'll review your employer coverage and help you determine the best path forward.
Can I have both Medicare and employer health insurance?
Yes. You can have Medicare and employer coverage at the same time. One will be primary (pays first), and the other will be secondary (pays the remaining costs). For employers with 20+ employees, employer coverage is primary. For employers with fewer than 20 employees, Medicare is primary.
Do I have to sign up for Medicare at 65 if I'm still working?
It depends on your employer's size. If you work for an employer with 20+ employees and have coverage through that job, you can delay Medicare Part B without penalty. If your employer has fewer than 20 employees, you must enroll in Medicare when you turn 65—it will be your primary insurance.
Can I have a Medicare Advantage plan and employer insurance?
Yes, you can have both. However, Medicare Advantage plans work differently from Original Medicare. If your employer coverage is primary, your Medicare Advantage plan would pay second. Talk to both your employer's benefits administrator and a Medicare agent to understand how the plans will coordinate.
What happens to my HSA when I enroll in Medicare?
Once you enroll in any part of Medicare, you can no longer contribute to an HSA. You can still use your existing HSA balance for qualified medical expenses, including Medicare premiums and out-of-pocket costs. Be aware that Part A can be retroactive up to 6 months—stop HSA contributions at least 6 months before applying for Medicare to avoid penalties.
Is COBRA considered creditable coverage for delaying Medicare?
No. COBRA is not coverage from "current employment," so Medicare is primary when you have COBRA. If you're on COBRA when you turn 65, you must enroll in Medicare Parts A and B during your Initial Enrollment Period. If you elect COBRA after retiring past 65, you have 8 months to enroll in Part B.
What's the Special Enrollment Period for Medicare after losing employer coverage?
You have an 8-month Special Enrollment Period to sign up for Medicare Part B and Part D after your employer coverage ends or your employment ends (whichever is first). There's no late enrollment penalty if you enroll during this period. You'll need proof of prior coverage from your employer.