Gluten can be confusing because there are 3 types of gluten issues. There is gluten intolerance, gluten allergy and celiac disease.
You are likely wondering which, if any you or someone you know is suffering from.
Gluten allergies or intolerances (sensitivities) are best diagnosed one of two ways. The fastest method is to have a blood test but these tests can show that you have an allergy or intolerance when, in fact, you do not. The second type of test is to do an elimination diet. There are two methods of elimination diets but the result is the same. You remove all potentially offending foods for 10 days and then add them back in on a set schedule to see if they cause systemic upset.
Celiac disease is a completely different issue. A GI specialist needs to perform specified blood work and will then schedule an endoscopy, if deemed necessary. The biopsy takes 10 to 15 biopsies of intestinal cells. This test is looking at the health of the cilia (small hairs) that line the interior of your intestines.