Understanding Cystatin C: Normal vs Optimal Ranges

?What is Cystatin C?

Cystatin C is a small protein produced at a constant rate by all nucleated cells and filtered freely by the kidneys. Unlike creatinine, cystatin C levels are not significantly affected by muscle mass, age, sex, or dietary protein intake, making it a more reliable and less biased marker of kidney filtration rate, especially in the early stages of chronic kidney disease.

!Why It Matters

Cystatin C-based eGFR equations (eGFRcys) are more accurate than creatinine-based equations in elderly patients, sarcopenic individuals, athletes with high muscle mass, and people with early CKD. Elevated cystatin C predicts cardiovascular events and mortality even in individuals with normal creatinine-based eGFR, suggesting it captures early kidney dysfunction not seen by standard tests.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• Usually no direct symptoms — detected through routine testing
• Advanced kidney disease: fatigue, oedema, reduced urine output, hypertension

How to Improve Your Levels

• 1Maintain blood pressure, blood sugar, and weight in optimal ranges
• 2Stay well hydrated
• 3Minimise nephrotoxic medications (NSAIDs, aminoglycosides, contrast agents)
• 4SGLT2 inhibitors significantly protect kidney function

When to Test

When creatinine-based eGFR may be misleading (low muscle mass, extreme body composition, elderly); advanced CKD management; cardiovascular risk stratification.

Related Biomarkers