Because there are several different types of biopsy procedures, your preparation will depend on your specific biopsy. For a skin biopsy, for example, you usually won't need to change what you eat or drink beforehand. However, for an open biopsy that requires general anesthesia, you will need to stop eating and drinking at least several hours before the procedure. If you are scheduled for a colonoscopy and possible colon biopsy, you will take laxatives and enemas according to your doctor's directions, and will have to modify your diet.
In general, even for a minor skin biopsy, it is helpful to remind your doctor about your allergies, your history of surgical procedures and your list of current medications, especially aspirin and blood-thinning medicines. If you are a woman and there is a possibility that you might be pregnant, tell your doctor before you have a biopsy.