Kidney & Electrolytes

eGFR Cystatin C Test -- Measure Your Kidney Filtration Rate

Estimated glomerular filtration rate (eGFR) is the gold-standard measure of kidney function. This version uses cystatin C rather than creatinine, making it less dependent on muscle mass, body composition, and age. It is especially valuable for people who are elderly, very muscular, underweight, or frail, where creatinine-based eGFR may be misleading.

Why Test eGFR Cystatin C?

This test is recommended when early kidney disease is suspected, when monitoring medications that can affect the kidneys, or when creatinine-based eGFR results are unclear. It gives a more precise estimate for patients with atypical body composition and supports early detection and monitoring of chronic kidney disease.

What Do High eGFR Cystatin C Levels Mean?

An eGFR above 90 mL/min/1.73 m2 generally indicates normal kidney function. Values between 60 and 89 may be normal depending on age and risk factors. No clinical concern is typically raised at these levels.

What Do Low eGFR Cystatin C Levels Mean?

An eGFR below 60 suggests reduced kidney function, potentially due to chronic kidney disease. Values below 15 indicate severe kidney failure that may require dialysis or specialised treatment. Low values can also be caused by dehydration, acute illness, or certain medications.

Symptoms to Watch For

  • Fatigue and weakness
  • Reduced urine output
  • Swelling in the legs or ankles
  • Nausea
  • Difficulty concentrating
  • Shortness of breath

Who Should Get Tested?

  • People with suspected or early-stage kidney disease
  • Patients on nephrotoxic medications
  • Elderly individuals or those with unusual body composition
  • Athletes who need a more accurate kidney assessment
  • Anyone with diabetes, hypertension, or cardiovascular disease

How to Prepare for Your Test

No fasting required. Ensure you are well-hydrated and not experiencing acute illness. Bring valid ID.

Frequently Asked Questions

What is a normal eGFR value?
A normal eGFR is above 90 mL/min/1.73 m2. Values between 60 and 89 may be acceptable depending on age. Below 60 warrants further investigation.
Why use cystatin C instead of creatinine for eGFR?
Cystatin C is produced at a constant rate regardless of muscle mass or diet, making the calculation more reliable in people who are elderly, very lean, or very muscular.
Can dehydration affect my eGFR result?
Yes. Dehydration can temporarily lower eGFR. For the most accurate result, make sure you are well-hydrated before the test.
How often should I monitor eGFR?
For general screening, annually is sufficient. If you have known kidney disease or are on medications affecting the kidneys, your doctor may recommend every 3 to 6 months.
NW

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Wellth

Our content is written and reviewed by Wellth, and fact-checked against peer-reviewed research and current Swedish clinical guidelines.

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Medical Disclaimer

The information on this page is provided for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. Wellth provides health information and testing services but is not a substitute for clinical care. Always consult a qualified healthcare provider if you have questions about a medical condition. If you are experiencing severe or urgent symptoms, contact your doctor or call 1177 Vårdguiden. Blood test results should be interpreted by a qualified healthcare professional in the context of your complete medical history.