Cystatin C

Cystatin C is a protein made by almost all cells in the body. Its level in the blood can show how well your kidneys are working. Cystatin C is more accurate than other kidney tests  such as creatinine as it is less influenced by muscle mass. This makes it a useful kidney marker for people with low muscle mass, like older adults, amputees, or those with muscle problems.

The Cystatin C test is often suggested when a doctor suspects kidney problems. However, the typical kidney tests, such as creatinine or creatinine clearance, may not provide a clear picture. It is also done when there are symptoms indicating kidney issues, such as fatigue, swollen ankles, feet, and hands, changes in urine output, unexplained weight loss, etc. It can also be done if there are risk factors like high blood pressure, diabetes, or a family history of kidney disease. Additionally, it is used to monitor kidney health in individual undergoing treatments that may affect the kidneys.

Elevated levels of cystatin C may indicate that the kidneys are not functioning properly, as they are unable to filter it efficiently. This can be an early warning sign of kidney disease such as chronic kidney disease (CKD) or acute kidney injury (AKI), often before other markers, like creatinine, show significant changes.

No special preparation is required for this test. Inform the doctor about all the medications or supplements being taken as they might affect the test results.  

Test result ranges are approximate and may differ slightly between labs. Talk to your doctor about your specific test results. The results will help them determine your medical condition and formulate an overall treatment plan. They may suggest lifestyle recommendations and medications if required to manage your condition.