The steps you will take to prepare for an ultrasound will depend on the area or organ that is being examined. Your doctor may tell you to fast for eight to 12 hours before your ultrasound, especially if your abdomen is being examined. Undigested food can block the sound waves, making it difficult for the technician to get a clear picture. For an examination of the gallbladder, liver, pancreas, or spleen, you may be told to eat a fat-free meal the evening before your test and then to fast until the procedure. However, you can continue to drink water and take any medications as instructed. For other examinations, you may be asked to drink a lot of water and to hold your urine so that your bladder is full and better visualized. Be sure to tell your doctor about any prescription drugs, over-the-counter medications, or herbal supplements that you take before the exam. It’s important to follow your doctor’s instructions and ask any questions you may have before the procedure. An ultrasound carries minimal risks. Unlike X-rays or CT scans, ultrasounds use no radiation. For this reason, they are the preferred method for examining a developing fetus during pregnancy.