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