Cystatin C is a superior marker for kidney function that provides more accurate results than creatinine, especially for people with unusual muscle mass or those needing precise kidney assessment.
Cystatin C is a small protein produced by all nucleated cells in the body and filtered by the kidneys. Unlike creatinine, cystatin C levels are not significantly affected by muscle mass, diet, age, or sex, making it a more reliable marker of kidney function in many situations. This test measures cystatin C and calculates an estimated glomerular filtration rate (eGFR) based on cystatin C, providing a more accurate assessment of how well your kidneys filter blood. It is particularly useful for athletes, very muscular or very thin individuals, elderly patients, and anyone needing a more precise kidney function assessment than standard creatinine-based testing provides.
Price
$16
Results
2-3 days
Lab Network
Quest
Fasting
Not Required
What's Measured
What This Test Measures
This test measures cystatin C levels in your blood and calculates an eGFR (estimated Glomerular Filtration Rate) based on cystatin C. The eGFR indicates how well your kidneys filter waste from your blood, with higher values indicating better kidney function.
Who Should Consider This Test
Athletes and bodybuilders (high muscle mass affects creatinine accuracy), elderly individuals (muscle mass decline affects creatinine), people with unusual body composition, those with borderline creatinine-based eGFR results, vegetarians and vegans (diet affects creatinine), and anyone needing precise kidney function assessment.
Health Insights
Conditions Screened
Related Symptoms
When to Get Tested
No fasting is required. This test can be taken at any time. It is often ordered alongside or instead of standard creatinine-based kidney function tests when more accuracy is needed.
Understanding Your Results
Cystatin C-based eGFR values above 90 mL/min/1.73m² indicate normal kidney function. Values of 60-89 suggest mildly reduced function, 45-59 moderate reduction, 30-44 moderate-severe reduction, 15-29 severe reduction, and below 15 indicates kidney failure. Results may differ from creatinine-based eGFR, and the more accurate value depends on individual factors.
What to Expect
After placing your order, you'll receive an email from Rupa Health (our lab order partner) within 24 business hours to sign a consent form and schedule your blood draw at a Quest Diagnostics location.
The blood draw typically takes just a few minutes. Results are usually available within 2-3 business days and will appear in your secure Justlabs dashboard.
Our results include reference ranges and easy-to-understand indicators showing whether your values are within normal limits.
Frequently Asked Questions
$16
Typical hospital cash price: $120–$200
+ $28 in standard lab & physician fees at checkout (no additional bills later)
$18 lab collection + $10 physician order
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