What Is a Carotid Intima-Media Thickness (CIMT) Test?

Medically Reviewed by James Beckerman, MD, FACC on February 14, 2024
3 min read

You have two carotid arteries in your neck that are responsible for supplying oxygen-rich blood to your head and brain. Like all arteries, carotid arteries are made up of three layers:

  • An outer protective layer called the adventitia
  • A muscular middle layer called the media
  • A smooth inner layer called the intima

A carotid intima-media thickness (CIMT) test is used to measure the thickness of your carotid arteries’ inner and middle layers. This information can help doctors know the extent of plaque buildup in your arteries and diagnose carotid artery disease before you have any symptoms.

A CIMT test is useful because people with carotid artery disease might not have any symptoms of the condition. Many times, a transient ischemic attack (TIA) or a stroke is the first sign a person has carotid artery disease. Both TIAs and strokes happen when part of your brain doesn’t get the blood flow and oxygen it needs. 

A TIA can last for just a few minutes or up to an hour. Symptoms usually go away within 24 hours, and people who have had a TIA go on to make a full recovery. Stroke symptoms last longer, and recovery for people who have had a stroke can vary greatly depending on the severity of the stroke. 

Even if you do not have any carotid artery disease symptoms, your doctor might order the test to check for any changes in your carotid artery thickness. You have a greater risk of having carotid intima-media thickening if you are Black, male, older, or have high blood pressure and cholesterol levels. Other risk factors include:

  • Diabetes
  • Obesity
  • Smoking
  • Lack of regular exercise
  • Family history of carotid artery disease

Early diagnosis and screening allow your doctor to understand your health condition and help you take steps to manage or prevent future heart disease and strokes.

A carotid intima-media thickness test uses an ultrasound to create images of your carotid artery. Your doctor will take several measurements of your carotid arteries on each side of your neck. 

You don’t have to do anything special to prepare for a CIMT test, but you should take off any necklaces or jewelry that might get in the way and consider wearing a comfortable, open-necked, or button-up shirt.

During the scan, you will be asked to lay with your head turned to the side. The ultrasound should not be uncomfortable, but you may be asked to move and turn your head in different directions so that a clear view of your carotid arteries on both sides of your neck can be seen. 

Carotid intima-media thickness can vary by age, gender, and ethnicity. Blacks and men often have thicker artery walls. 

Normal carotid intima-media thickness for middle-aged, healthy adults is usually between 0.6-0.7 millimeters. 

Test results showing a thickness of more than 1.0 millimeter may mean you have a high risk of cardiovascular disease. 

Results that place you in less than the 25th percentile can mean you have a lower risk of cardiovascular disease.

Results between the 25th and 75th percentiles are considered normal and don’t necessarily indicate a greater or lesser risk of cardiovascular disease.

Depending on your CIMT test results, your doctor might prescribe certain medications to lower your blood pressure and cholesterol, or suggest steps you can take to improve your diet and lead a more heart-healthy lifestyle.