Cystatin C
Cystatin C is a protein produced uniformly by all cells and filtered by the kidneys. Unlike creatinine, it does not depend on muscle mass, so it is often a more accurate measure of filtration.
| Rating | Range | What it means |
|---|---|---|
| Good | below 1 mg/L | Within the reference range. |
| Worth improving | 1 – 1.3 mg/L | Mildly elevated — assess eGFR. |
| Talk to a doctor | 1.3 mg/L and above | Elevated — reduced kidney function; consult. |
This marker also has 4 age- or sex-specific range sets in the app — the table shows the general one.
Why it matters
KDIGO recommends combining creatinine + cystatin C for the most reliable eGFR (eGFRcr-cys).
If it’s low
Low/normal cystatin C is favorable — good filtration.
If it’s high
High cystatin C means poorer kidney filtration (lower eGFR) — similar to creatinine, but more independent of muscle.
What to do
Cystatin C is not a lifestyle marker. It is used to confirm the kidney estimate; the measures are as for eGFR (control of blood pressure/sugar, hydration).
Read together with
eGFR · Creatinine · Microalbumin (urine)
Part of the guide: Kidneys & electrolytes →
Articles about this marker
This content is for information only and is not a substitute for medical advice. Talk to your doctor about your results.
Your number, not the average
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