...From St John's
How long do I need to eat gluten before getting the blood work and biopsy?
4 weeks of 4 slices of bread a day, or 4 weeks of 2 servings of pasta a day is thought to be enough stimulation. However, with a challenge there is a risk that the abnormalities will not be apparent.
Stephen Holland, M.D.....
Read more: http://coeliac.proboards.com/thread/3475/gluten-long-biopsy#ixzz4jcdoY8RW
....Ensure adequate gluten intake prior to testing with advice from dietician if necessary.
10-15g gluten per day is required for adequate intake in most children (eg. 2-3g gluten are
contained in one medium bread slice, one Weetabix or Shredded Wheat, two rusks or
digestives and 4 tablespoons of cooked pasta)...