Ultrasound is a noninvasive imaging test that shows structures inside your body using high-intensity sound waves. Healthcare providers use ultrasound exams for several purposes, including during pregnancy, for diagnosing conditions and for image guidance during certain procedures.

During an ultrasound, a healthcare provider passes a device called a transducer or probe over an area of your body or inside a body opening. The provider applies a thin layer of gel to your skin so that the ultrasound waves are transmitted from the transducer through the gel and into your body.

The probe converts electrical current into high-frequency sound waves and sends the waves into your body’s tissue. You can’t hear the sound waves.

Sound waves bounce off structures inside your body and back to the probe, which converts the waves into electrical signals. A computer then converts the pattern of electrical signals into real-time images or videos, which are displayed on a computer screen nearby.

The preparations will depend on the type of ultrasound you’re having. Some types of ultrasounds require no preparation at all.

For ultrasounds of the pelvis, including ultrasounds during pregnancy, of the female reproductive system and of the urinary system, you may need to fill up your bladder by drinking water before the test.

For ultrasounds of the abdomen, you may need to adjust your diet or fast (not eat or drink anything except water) for several hours before your test.

In any case, your healthcare provider will let you know if you need to do anything special to prepare for your ultrasound.

Preparation for an ultrasound varies depending on what body part you’ll have scanned. Your provider may ask you to remove certain pieces of clothes or change into a hospital gown.

Ultrasounds that involve applying the transducer (probe) over your skin (not in your body), follow these general steps:

✔ You’ll lie on your side or back on a comfortable table.
✔ The ultrasound technician will apply a small amount of water-soluble gel on your skin over the area to be examined. This gel doesn’t harm your skin or stain your clothes.
✔ The technician will move a handheld transducer or probe over the gel to get images inside your body.
✔ The technician may ask you to be very still or to hold your breath for a few seconds to create clearer pictures.
✔ Once the technician has gotten enough images, they’ll wipe off any remaining gel on your skin and you’ll be done.

An ultrasound test usually takes 30 minutes to an hour. If you have any questions about your specific type of ultrasound, ask your healthcare provider.

The time it takes to get your results depends on the type of ultrasound you get. In some cases, such as prenatal ultrasound, your provider may analyze the images and provide results during the test.

In other cases, a radiologist, a healthcare provider trained to supervise and interpret radiology exams, will analyze the images and then send the report to the provider who requested the exam. Your provider will then share the results with you or they may be available in your electronic medical record (if you have an account set up) before your provider reviews the results.