Home › Biomarkers › Cystatin C
In a large study, researchers looked at people whose kidney filtration had been estimated at 45 to 59 ml per minute per 1.73 m² based on creatinine. A calculation using creatinine and cystatin C together correctly reclassified 16.9% of them as having a filtration of 60 ml or more per minute.[1]
On this page you can read what cystatin C is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best looked at alongside it.
Also known as: cystatin C, serum cystatin C. At the lab: CYSTAT.
Cystatin C is a filtration marker. Doctors use it to estimate the filtration rate of your kidneys, known as the glomerular filtration rate (GFR). This rate is expressed in ml per minute per 1.73 m² of body surface area.[1]
Researchers developed calculation formulas using cystatin C alone and using cystatin C together with creatinine. They did this with data from 5,352 participants in 13 studies. They then tested the formulas in 1,119 participants from 5 other studies, whose filtration had actually been measured.[1]
Creatinine-based estimates of filtration are used as standard. However, they are not precise. As a result, a long-term kidney condition may be diagnosed too often.[1]
With creatinine and cystatin C together, the estimate was more often close to the measured filtration. The share of estimates that differed by more than 30% from the measured value was 8.5%, compared with 12.8% with creatinine alone and 14.1% with cystatin C alone.[1]
In people whose creatinine-based estimated filtration was 45 to 74 ml per minute per 1.73 m², the combination did better at classifying measured filtration as below 60 or as 60 and above. The researchers therefore see the combination as a possibly useful confirmatory test.[1]
Labplusarts, the lab BioProfile works with, uses a reference range of 0.64 to 1.12 mg/L for cystatin C. The lab calls a value between those limits normal.[2]
| Value | What it can mean | Who it is for |
|---|---|---|
| 0.64 to 1.12 mg/L[2] | The lab calls this value normal | Who has the CYSTAT test done at this lab |
Source: the Labplusarts lab's reference range for cystatin C (CYSTAT), list dated 24 September 2026. The sources on this page give no limits of their own for cystatin C itself.[2]
In the source, cystatin C is used to estimate how well your kidneys filter. That is why a high value is not read on its own. Together with creatinine, cystatin C gave the most accurate estimate in the research, and that combination can help confirm a long-term kidney condition. A doctor looks at which values belong alongside it.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Cystatin C is a filtration marker. Its value is linked to how well your kidneys filter, which is why it can be used to estimate that filtration.[1]
In the study, the cystatin C and creatinine measurements were traceable to primary reference materials. This tied the results to a fixed standard, which matters when you use them in a calculation formula.[1]
Cystatin C is included in BioProfile 150.[3]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
