This is usually an outpatient procedure. Samples of the lining of your small intestine will be studied under a microscope to look for damage and inflammation due to celiac disease. It is recommended that the doctor take at least four samples in order to obtain an accurate diagnosis.
For biopsy results to be accurate, you must be eating gluten (at least four slices of bread per day) for one to three months prior to the procedure. Check with your doctor to confirm this.