An accurate picture of your kidney function.
Cystatin C estimates the filtration function of your kidneys, independent of your muscle mass. It is a valuable addition or alternative when creatinine is difficult to interpret.
Also known as: cystatin c, cystatine c, kidney function, cystatin C eGFR
Interpreted by BIG-registered doctors
How Bloodworks works
Order online
Choose your package and preferred location
Receive your lab form
Within 24 hours by email, with appointment planner
Schedule your blood draw
Or choose a walk-in location
Blood draw
Takes just a few minutes
Receive your report
Securely, typically within 2 working days from our physicians
Background
What is Cystatin C?
Cystatin C is a small protein produced at a constant rate by virtually all cells in your body. It is filtered out of the blood by the kidneys and then almost entirely broken down. If the kidneys filter less well, the amount of cystatin C in the blood rises. A single measurement therefore gives a good impression of your kidneys' filtration function.
What makes cystatin C special is that its production barely depends on muscle mass, sex or diet. Whereas the creatinine level is strongly influenced by how much muscle you have, cystatin C gives a more stable picture. That is why a cystatin C-based eGFR is also calculated, which is often more accurate in people with high or low muscle mass.
In brief
Small protein
Produced by all cells at a constant rate
Filtration
The kidneys filter cystatin C from your blood
Muscle-independent
Barely influenced by muscle mass, sex or diet
Accurate eGFR
Often gives a more precise estimate of the filtration rate
Common reasons to test
When can insight into your Cystatin C be valuable?
Below are some situations in which measuring Cystatin C can provide insight.
An accurate kidney picture
Cystatin C gives a more precise estimate of the filtration function than creatinine alone, and is a good addition when you want certainty about your kidney function.
With high or low muscle mass
Strength athletes with high muscle mass, or people with low muscle mass, often have a creatinine value that is difficult to interpret. Cystatin C then gives a more reliable picture.
Confirming a borderline result
If your creatinine or eGFR is just abnormal or doubtful, cystatin C helps to confirm whether there really is reduced filtration function.
With high blood pressure or diabetes
High blood pressure and diabetes place a burden on the kidneys over time. Cystatin C helps to monitor kidney function accurately.
With long-term medication use
Some medicines are excreted via the kidneys or place a burden on them. An accurate filtration estimate is then relevant.
Tracking a value over time
For kidney function the trend is often more informative than a single measurement. Re-testing makes a change visible.
What your result means
How do we read your Cystatin C level?
Cystatin C is measured in milligrams per litre (mg/L). The laboratory states the reference values that apply there alongside your result. Unlike creatinine, cystatin C is barely influenced by muscle mass, age or diet, which makes the value more stable to interpret.
A low value
A low cystatin C value is consistent with good filtration function and is usually reassuring. Our doctor provides explanation and context with your result.
A normal value
A cystatin C within the laboratory's reference values gives a reassuring picture of the filtration function at this moment. It remains a snapshot: for kidney function, the development over time is often more informative than a single measurement.
An elevated value
An elevated cystatin C may point to reduced filtration function of the kidneys. Because cystatin C is barely sensitive to muscle mass, the value is often more reliable than creatinine alone. Even so, a single measurement is not a diagnosis: a strongly overactive thyroid, inflammation or the use of corticosteroids can also influence the value. Our doctor explains what your value means and whether a repeat test or follow-up via your GP is customary.
How we interpret your result
Our doctors interpret your cystatin C against the laboratory's reference values and your personal context, such as age, lifestyle, medication use and any known conditions. Where useful, they place the value alongside your creatinine and eGFR.
Related tests
Often combined with Cystatin C.
A single marker gives one perspective. For a broader picture you can combine Cystatin C with a theme package or related markers.
Frequently asked questions
Everything you want to know
What is the difference between cystatin C and creatinine?
Both are filtered by the kidneys and say something about the filtration function. The difference is that the creatinine value strongly depends on your muscle mass, whereas cystatin C is barely influenced by it. With high or low muscle mass, cystatin C therefore often gives a more accurate picture.
Do I need to fast for a cystatin C test?
No, you do not need to fast for cystatin C. Do drink water normally, as you usually would.
Why is cystatin C interesting for athletes?
Strength athletes often have high muscle mass, which raises the creatinine value without anything being wrong with the kidneys. Cystatin C does not depend on muscle mass and therefore gives a more reliable picture of kidney function.
Can a single elevated value mean kidney disease?
No. A single measurement is not a diagnosis. Besides kidney function, a strongly overactive thyroid, inflammation or the use of corticosteroids can influence the value. For kidney function, the trend over time is usually more important than a single value.
Does exercise or creatine use affect the result?
Unlike creatinine, cystatin C is barely influenced by a heavy training session shortly before the draw or by creatine supplements. That makes it an attractive marker for active people.
What do I do with my result?
You receive a PDF report with your values and a personal explanation from a doctor. What you do with it, such as discussing it with your GP, remains entirely your choice.
Ready for insight into your kidney function?
For €89 you receive your cystatin C including personal explanation from a doctor, typically within 2 working days. No referral required.
Order Cystatin C for €89 →Want to test multiple markers at once?
Combine Cystatin C with other markers via Bloodworks Select. Blood draw costs are waived from €225.
89,-
All-in, blood draw included