Cystatin C is a protein produced by the body's nucleated cells. In the kidney's glomeruli (capillary network), cystatin C is eliminated by filtration.
Cystatin C value can be measured in order to get an estimate of kidney function. The value is not affected by age, gender and muscle mass or diet. A high value of cystatin C may indicate poorer kidney function, as it may mean that the kidneys are not filtering out cystatin C as they should.