eGFR (Cystatin C) · low result
What does a low eGFR (Cystatin C) mean?
Short answer
A low cystatin C–based eGFR means the kidneys are filtering below expected for age. Because cystatin C is not inflated by muscle mass, meat or creatine, it is a more trustworthy kidney signal than creatinine in athletes, older adults and people with low muscle mass — though thyroid disease, steroids and obesity can lower it without kidney change. Below 60 for three months defines chronic kidney disease.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
When does this result need same-day care?
- A sharp fall from a recent value, very little urine, or swelling with breathlessness — same-day care
What is the normal range for eGFR (Cystatin C)?
- age 18+: 60.0 – 120 mL/min/1.73m2
Sustained values below 60 can indicate chronic kidney disease.
Full reference table, citations and testing options: eGFR (Cystatin C) biomarker page.
What are the common causes of low eGFR (Cystatin C)?
- Chronic kidney disease: diabetes, hypertension, glomerular disease, polycystic kidney disease
- Acute kidney injury: dehydration, NSAIDs, contrast, infection
- Hyperthyroidism, high-dose corticosteroids (raise cystatin C, lower this eGFR)
- Obesity, smoking, inflammation (modest)
- Normal aging (eGFR falls ~1 mL/min per year after 40)
What symptoms go with low eGFR (Cystatin C)?
- Usually none until well below 30
- Fatigue, swelling, foamy urine, nocturia, itching as kidney disease progresses
What do clinicians usually check next?
- Creatinine-based eGFR at the same draw; the combined equation is the most reliable single number
- Urine albumin-to-creatinine ratio
- Blood pressure, A1c, TSH, medication review (NSAIDs, PPIs, lithium)
- Repeat in 3 months to confirm before any CKD label; nephrology referral below 45 or if falling fast
Follow-up tests available at TestWell: TSH (Thyroid Stimulating Hormone) ($26.99), TSH + Free T4 ($27.99).
How do you recheck eGFR (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 |
| Renal Panel | Test · 10 biomarkers | $23.99 | No | 2–4 business days |
Common questions
My creatinine eGFR is normal but the cystatin C eGFR is low — which is right?
Possibly the cystatin C one: creatinine underestimates kidney disease in people with low muscle mass. The reverse mismatch happens in muscular people. When they disagree, clinicians use the combined equation and the urine albumin to decide.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.