What Is a Doppler Ultrasound?

Medically Reviewed by Carmelita Swiner, MD on November 30, 2022
4 min read

Sometimes, doctors find a way to use technology that hits all the right notes -- it’s easy on your body, gives fast results, and doesn’t cause any side effects. That’s just the case with Doppler ultrasound, which gives doctors a way to see what’s going on inside your body without X-rays or injections.

Instead, it turns sound waves into images. Your doctor can use it to check for issues with blood flow, such as clots in your veins or blockages in your arteries.

It’s one of the main ways to test for deep vein thrombosis (DVT) -- a condition where blood clots form in veins deep in your body, usually in your legs. DVT can lead to more serious problems, such as a clot in your lungs. It can be life-threatening. So it’s important to get tested if you have symptoms.

If you have symptoms of DVT, such as swelling or pain in your leg, your doctor may use Doppler ultrasound to see what’s going on. The images show where blood slows down or stops, which could mean you have a clot.

Doppler ultrasound is very effective in a lot of cases, but it’s not good at finding clots in your pelvis or the small blood vessels in your calf.

In addition to finding clots, Doppler ultrasound can be used to:

  • Check blood flow in your veins, arteries, and heart 
  • Look for narrowed or blocked arteries
  • See how blood flows after treatment
  • Look for bulging in an artery which is called an aneurysm

When it’s done on your belly, it can help find:

It can also be used to check on blood flow to your baby during pregnancy.

Generally, it helps to wear loose-fitting clothes to the test, though your doctor may ask you to change into a gown. Also, you may want to leave jewelry at home, since you’ll have to remove it from any area to be tested.

If you’re getting the test for DVT or other issues in your legs, you won’t need to do anything else.

For a Doppler ultrasound on your belly, your doctor may tell you to fast for 6 to 12 hours before the test. That means you won’t be able to eat or drink anything during that time. You’ll only be able to drink a small amount of water to take your regular medicines.

For women getting a pelvic Doppler ultrasound, you’ll have to drink 32 ounces of water 1 hour before the exam. You need to have a full bladder for the test to be effective.

You will lie on a table, usually on your back. Your doctor or a technician will rub a gel on the area to be tested. This helps the sound waves travel and gives you better results.

Next, they will press a small device against your skin. It looks like a microphone or a wand.

As they move the device around, it sends sound waves into your body. The waves bounce off your blood cells, organs, and other body parts, then back to the device. You’ll feel some pressure from the device, but unless you have tenderness, it won’t hurt.

A computer takes all the sound waves and turns them into moving images that you can see live on a screen. Once the test is done, you wipe the gel from your body, and you’re all set. It usually takes about 30 to 60 minutes.

You can get results from a Doppler ultrasound very quickly. Sometimes, the person who runs the test is trained to do ultrasounds but isn’t a doctor. Even then, the images are available right away for your doctor to review.

This test is very safe, painless, and doesn’t use radiation.

Your doctor will let you know what all the images mean. If you had the test done to check for DVT, they will tell you what the images show about your blood flow and tell you the next steps to take.

If you do have a clot, you may have more than one Doppler ultrasound over a few days to see whether the clot grows or any new ones show up.