FNAs are usually performed in the doctor's office as outpatient procedures. Anesthetics aren't always needed, but sometimes numbing medications (called local anesthetics) are used. Due to the thinness of the needle used for the biopsy, anesthetics may hurt more than the biopsy itself. It usually takes about 15 seconds to get a biopsy sample. Generally, procedures take between 20 and 30 minutes from start to finish when ultrasounds are used.