Cystatin C test
Informed by recognized medical guidance
Overview
The cystatin C test is a blood test that measures a protein called cystatin C. Your body makes this protein, and healthy kidneys remove it from your blood. When the kidneys are not working well, the level of cystatin C rises. This test gives your doctor a more accurate picture of your kidney function than some other tests, especially in certain situations.
Key facts
- Cystatin C levels are not affected by your muscle mass, so the test can be more accurate for older adults, people with muscle wasting, or those on special diets.
- The test is often used together with a creatinine test to confirm or clarify how well your kidneys are filtering waste.
- Results from the cystatin C test help your doctor diagnose chronic kidney disease (CKD) and decide on the best treatment plan.
The cystatin C test is becoming more common, especially for people whose creatinine tests may not be reliable, such as those with diabetes, heart failure, or after a kidney transplant.
It is used for anyone who needs a precise check of kidney function, including older adults, people with long-term conditions like high blood pressure or diabetes, and those who have had a kidney transplant.