Cystatin C

Cystatin C is protein found in the blood that helps measure kidney function. It’s produced at a steady rate by most cells in the body and then filtered out by the kidneys. By measuring how much cystatin C is in the blood, clinicians can estimate how well the kidneys are working. When kidney function is good, cystatin C levels are low because the kidneys filter it out efficiently. High levels can suggest the kidneys aren’t filtering well, which may indicate kidney disease. Cystatin C may be especially useful because it’s less affected by factors like muscle mass, potentially making it a more accurate measure of kidney health than other tests, like creatinine.