If you get your insurance coverage through your job, federal law governing pre-existing conditions applies. Your insurer will be permitted to "look-back" to see if you received any medical attention or diagnosis during the six-month period immediately preceding your enrollment. The insurer will use this information to determine what medical conditions you already had when you enrolled. So if you received medical care for a particular condition more than six months prior to enrollment, then that condition is not pre-existing under federal law.
If you have an individual health insurance policy, federal law will not apply, so insurers may be permitted to "look-back" at your claims history for the past year, eighteen months or even longer when determining if you have any pre-existing health conditions. Rules governing pre-existing conditions and "look-back" periods for individual policies vary by state.
Source:
United States Department of Labor, Employee Benefits Security Administration. "Frequently Asked Questions About Portability of Health Coverage and HIPAA." Accessed June 3, 2008.
