If you and a spouse have different health insurance but have never designated one as primary or secondary could this cause problems when you do designate primary or secondary?

If you have insurance through your employer, and you are the policy holder,(the insurance is in your name) this insurance will be primary for you, and your spouses insurance policy will be secondary.

The insurance policy thru your spouse's employer, (your spouse is the policy holder, or the insurance is in their name), this would be primary for your spouse, and your policy would be their secondary.

Here's the phamplet from Medicare http://www.medicare.gov/Publications/Pubs/pdf/02179.pdf