Cystatin C

Understanding the marker

Cystatin C is a protein removed from the blood by the kidneys. Its level can complement creatinine when estimating kidney filtering and is less affected by muscle mass.

Cystatin C can be used to calculate an estimated filtration rate, or eGFR. Medicines, thyroid function and inflammation can affect the result. Creatinine and cystatin C provide complementary information; neither is always the better estimate in every situation.

What does high Cystatin C mean?

A high cystatin C concentration may reflect reduced kidney filtering. The eGFR estimate, creatinine, any medicines and relevant thyroid or inflammation results help assess other influences.

What does low Cystatin C mean?

A low cystatin C concentration does not usually suggest reduced kidney filtering. It is read with the laboratory's eGFR estimate and other relevant kidney results.