Kidney

Cystatin C

Cystatin C. Measured in clinic at The Wellness in Marylebone, read by a doctor.

What It Is

Cystatin C is a small protein produced at a steady rate by almost every cell in the body and cleared from the blood by the kidneys. Its level rises as kidney filtration slows, which makes it a marker of kidney function.

Why It Matters

Unlike creatinine, cystatin C is not influenced much by muscle mass, so it can give a cleaner view of kidney function in very muscular, very slim or older people. Clinicians often use it to confirm or refine an eGFR based on creatinine.

What Results Can Suggest

A raised cystatin C can suggest that the kidneys are filtering less efficiently than expected. Thyroid conditions and some medicines can also influence the level. A doctor can weigh it alongside creatinine, eGFR and your history, so discuss the result with one.

This page is general information, not medical advice and not a substitute for a consultation. Reference ranges vary between laboratories, and results should always be interpreted by a doctor who knows your history.