Cystatin C blood test
Quick answer: A cystatin C test measures a small protein filtered by the kidneys, giving another estimate of kidney function. Doctors use it when creatinine may be misleading, for example in people with very high or low muscle mass.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed.
How the test is done
- 1You sit and a band is tied around your arm
- 2A needle draws blood into a tube
- 3The lab measures cystatin C
- 4An eGFR may be calculated, sometimes combined with creatinine
What your results can mean
Reading your report
Normal ranges differ between labs and by age and sex, so discuss your result with your doctor.
If the result is outside the usual range
A high level can be seen with reduced kidney function, even when creatinine is still normal. Thyroid problems, steroid medicines and inflammation can also affect it.
Who usually has this test
People in whom creatinine may be misleading, such as those with very high or low muscle mass, older adults and some children.
Risks and aftercare
A small bruise may develop; otherwise no special care is needed.
Names and options
Also called: cystatin C
Listed by the hospital as
- CYSTATIN C, SERUM
Questions about this test
How is cystatin C different from creatinine?
Creatinine depends on muscle mass, while cystatin C is less affected by it. This makes cystatin C helpful when muscle mass is unusual.
Can cystatin C detect early kidney disease?
It can sometimes pick up reduced kidney function earlier than creatinine. Your doctor uses it with other tests.
Do thyroid problems affect cystatin C?
Yes. An overactive thyroid can raise it and an underactive thyroid can lower it.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.