Also known as: Cystatin C with eGFR, Cystatin C Kidney Function Test
The short answer
Kidney Function Test (Cystatin C) measures Cystatin C and eGFR (Cystatin C-based) from a standard blood draw. At TestWell it costs $36.99 plus a $6 lab fee, needs no fasting, and results post in 2–4 business days. Physician-authorized with no doctor's visit or insurance needed; draw at Quest or Labcorp.
Hospital Lab
$180
cash pay
Other Labs
$60
+ lab fees
TestWell
$36.99
+ $6 lab fee
Cystatin C is a protein produced at a constant rate by all cells in the body and filtered by the kidneys. Unlike creatinine, it's not significantly affected by muscle mass, diet, age, or gender, making it a more accurate marker of kidney function in many populations including the elderly, athletes, and those with very high or low muscle mass. The eGFR calculated from cystatin C is increasingly recommended as a complementary or alternative measure to creatinine-based eGFR.
Measures cystatin C, a protein filtered by the kidneys at a constant rate, to estimate glomerular filtration rate (eGFR). Because cystatin C is not affected by muscle mass, diet, or age the way creatinine is, it provides a more accurate picture of kidney filtration — especially in people with low muscle mass, obesity, or early-stage kidney disease where creatinine may look falsely normal.
People with diabetes, high blood pressure, or a family history of kidney disease; anyone who received a borderline creatinine result and wants confirmation; older adults or those with low muscle mass whose creatinine may underestimate kidney decline; and patients monitoring kidney health while on medications that stress the kidneys.
Sample Type
Blood draw
Fasting
Not required
Results In
2–4 business days
Performed At
Quest or Labcorp
2 biomarkers tested · 1 measured, 1 calculated from them
Your Kidney Function Test (Cystatin C) results will include values for each of the 2 biomarkers tested, along with reference ranges. Results are reviewed by a licensed physician before being released to your secure portal.
If any values fall outside the normal range, your report will include guidance on what that may mean and recommended next steps. You'll receive an email notification when your results are ready, typically within 2–4 business days.
Typical reference range layout
Lab reports show where your value sits relative to established reference intervals—your physician interprets this in context for you.
No fasting required.
A Kidney Function Test (Cystatin C) test costs $36.99 at TestWell — $42.99 all-in when ordered alone, because the $6 lab processing fee is charged once per order, with no draw fee or physician fee added. Hospital outpatient labs typically bill around $180.00 self-pay for the same test, and often more. With insurance, what you pay depends on your deductible and your plan's negotiated rate; TestWell's price is fixed before the draw and is HSA/FSA-eligible.
| Where you order | Price | One test, all-in | Notes |
|---|---|---|---|
| TestWell (drawn at Quest or Labcorp) | $36.99 | $42.99 | Includes the one $6 lab processing fee, charged once per order |
| Hospital outpatient lab, self-pay (typical) | $180.00 | $180.00 | Reference figure; hospital charges vary widely by facility and are often higher |
Lab test codes: Quest test code 94588 · Labcorp test no. 121265 · BioReference code J013-4. Competitor prices are read from the linked public pages and re-checked regularly; the labs' sites may add taxes or change prices without notice.
Compare more: Quest Diagnostics price list · Labcorp price list · Quest vs Labcorp · Lab test price checker
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
TestWell Price
$36.99
+ $6 lab processing fee at checkout
No insurance needed · HIPAA compliant
Better value: the Kidney Health Panel
Save $36.97This test is part of the Kidney Health Panel — 4 tests · 36 biomarkers for $64.99, $36.97 less than à la carte.
$64.99$101.96
4 tests · 36 biomarkers
Frequently ordered together
Customers who ordered Kidney Function Test (Cystatin C) also added these for a more complete health picture.
Not sure where to start?
Kidney Function Test (Cystatin C)
$36.99