Cystatin C

Does this test have other names?

No.

What is this test?

This test measures the amount of a protein called cystatin C in your blood.

Your body makes cystatin C constantly, and the protein is found in different fluids, including blood, spinal fluid, and breast milk. When your kidneys are healthy, they filter cystatin C out of the blood so it can be excreted in your urine.

This is a relatively new blood test to look at your kidney health.

Why do I need this test?

You may need this test if your doctor suspects that you have kidney problems.

You may also need this test if you are at an advanced age and your doctor wants to find out your risk for heart complications. But this type of testing is not yet routinely done.

What other tests might I have along with this test?

Your doctor may also order other tests to find out how well your kidneys filter toxins out of your blood. One of these tests is blood creatinine level.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

If you have an abnormally high concentration of cystatin C in your blood, it means you may have a kidney condition, such as chronic kidney disease. More than half of people older than 80 have elevated cystatin C levels.

Higher levels of cystatin C may also be caused by diabetes, hyperthyroidism, or hypothyroidism.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Using steroids can affect your results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.