How much gluten food does a patient need to eat before taking a celiac panel blood test? how far in advance does she need to eat gluten food? thanks!

Sometimes none: A celiac "panel" should look for several things and some of those will be positive in people with celiac disease without any exposure to gluten at or before the time of the test. Certain antibodies will only be positive if you have been exposed to gluten a day or so before the study, but they do not define celiac disease.

Basics: If you consume the equivalent of a slice of bread daily for 3 weeks prior to testing it will be enough to assure the tests will reflect your gluten status. Totally avoiding gluten does interfere with the testing.