I'm 74 years old. I have health coverage through my wife’s job. I also have Medicare. When I go to the doctor or have tests done, can I just use my insurance card from my spouse's plan, or must I use both? One doctor's office says work insurance is primary, another says Medicare is primary.

I've been telling them to use just the work insurance. I've received bills for doctor visits and tests even though they're in-network and covered. When I asked why, they told me it's because I have Medicare. Can you please clarify?

If Medicare is your primary coverage, the workplace plan only pays for its covered services if they aren’t covered by Medicare. (And anything not covered by Medicare or the workplace plan, you pay for out of pocket.)

When you're insured by Medicare and by a workplace plan, which is primary depends on the size of the workplace plan.

In general:

If you're 65 or older and covered through your current job or your spouse's current job for an employer with 20 or more workers, the workplace plan pays first and Medicare pays second. (Employers with 20 or more workers must offer all current employees the same health benefits regardless of age. If their plan covers employees' spouses, it must offer the same coverage to all spouses, regardless of age.)

But if the employer has fewer than 20 workers, Medicare pays first — unless the workplace plan is part of a "multi-employer' group health plan. In that case, the group plan pays first and Medicare pays second.

You need to ask the workplace insurer which rules apply to you.

The bottom line

If you have health insurance through a current job when you become Medicare-eligible at 65, it's vital to find out if Medicare is your primary coverage.

More information

bit.ly/Medicare-who-pays-first