Cystatin C, Serum

Why Is This Test Done?

Your doctor may order a cystatin C test to evaluate kidney function, especially if you have symptoms like fatigue, swelling, or changes in urine output. It can also be used in people with diabetes, high blood pressure, or a family history of kidney problems. Some doctors use it to help determine how well your kidneys are working, particularly in people with chronic kidney disease (CKD).

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure cystatin C levels. No special preparation is needed, but you may be asked to avoid certain medications or foods for a short time if instructed by your doctor.

What Do Results Mean?

Higher than expected cystatin C levels may suggest kidney problems, while lower levels might indicate other health conditions or medications affecting it. Your doctor will compare your results with your medical history and other tests to interpret them accurately.

Common Reasons for Testing

Cystatin C is sometimes used to monitor kidney function in people with chronic conditions like diabetes or high blood pressure. It can also help track kidney disease progression or guide treatment decisions, especially in people with mild to moderate kidney issues.