Cystatin C · high result
What does a high Cystatin C mean?
Short answer
High cystatin C means the kidneys are filtering less than expected. Because cystatin C is produced by all cells at a steady rate and, unlike creatinine, is not inflated by muscle mass, meat intake or creatine supplements, a high value is a more reliable kidney signal in athletes, older adults and people with low muscle mass. Thyroid disease, steroids, obesity and smoking can nudge it up independently of the kidneys.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
When does this result need same-day care?
- A sharp rise from a recent baseline, or high cystatin C with very little urine output or severe swelling — same-day care
What is the normal range for Cystatin C?
- age 18–49: 0.550 – 1.00 mg/L
- age 50+: 0.610 – 1.21 mg/L
Often reflects reduced kidney function. Less affected by diet and muscle mass than creatinine.
Full reference table, citations and testing options: Cystatin C biomarker page.
What are the common causes of high Cystatin C?
- Reduced kidney filtration — chronic kidney disease from diabetes, hypertension, glomerular disease
- Acute kidney injury (dehydration, medications, contrast)
- Hyperthyroidism, high-dose corticosteroids
- Obesity, smoking, inflammation, some cancers (modest increases)
- Older age
What symptoms go with high Cystatin C?
- Usually none until kidney function is substantially reduced
- Fatigue, ankle swelling, foamy urine, nocturia as kidney disease progresses
What do clinicians usually check next?
- Cystatin C–based eGFR alongside the creatinine-based eGFR; guidelines favor the combined creatinine–cystatin C equation when precision matters
- Urine albumin-to-creatinine ratio — the other half of kidney staging
- Blood pressure, A1c, TSH
- Repeat in 3 months to confirm chronicity before any CKD label
Follow-up tests available at TestWell: TSH (Thyroid Stimulating Hormone) ($26.99), TSH + Free T4 ($27.99).
How do you recheck Cystatin C?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Kidney Health Panel | Panel · 4 tests | $64.99 | Yes | 2–4 business days |
| Total Body Panel | Panel · 49 tests | $499.99 | Yes | 5–10 business days |
| Kidney Function Test (Cystatin C) | Test · 2 biomarkers | $36.99 | No | 2–4 business days |
Common questions
Why is my cystatin C high but creatinine normal?
Creatinine can read falsely reassuring in people with low muscle mass — older adults, small-framed people, those who are ill — so cystatin C may be catching real reduced filtration the creatinine missed. Thyroid disease and steroids also raise cystatin C without kidney change, so those are checked.
Is cystatin C better than creatinine for kidney function?
It is more accurate in the situations where creatinine is unreliable — high or low muscle mass, creatine supplements, high meat intake. Guidelines recommend using both together when a precise eGFR matters.
Sources
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.