Cystatin C levels: what's normal, high and low
A small protein cleared by the kidneys. An alternative kidney-function marker, especially useful when muscle mass is unusual.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Cystatin C is measured with a standard blood draw; no fasting is needed. A typical reference range is 0.550 – 1.00 mg/L (age 18–49; more bands below). At TestWell it's $36.99 all-in as Kidney Function Test (Cystatin C), results in 2–4 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- mg/L
- Sample
- Blood draw
- Fasting
- Not required
- Results
- 2–4 business days
- Price
- $36.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Cystatin C Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18–49 | 0.550 – 1.00 mg/L |
| age 50+ | 0.610 – 1.21 mg/L |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Cystatin C result may mean
Often reflects reduced kidney function. Less affected by diet and muscle mass than creatinine.
What a high Cystatin C means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
What does a high Cystatin C mean?
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.
Common causes of a 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
Ordered from most to least common.
Symptoms that can go with it
- Usually none until kidney function is substantially reduced
- Fatigue, ankle swelling, foamy urine, nocturia as kidney disease progresses
What 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 at TestWell: TSH (Thyroid Stimulating Hormone) ($26.99), TSH + Free T4 ($27.99).
Seek care promptly if
- A sharp rise from a recent baseline, or high cystatin C with very little urine output or severe swelling — same-day care
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.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Cystatin C test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Cystatin C is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Kidney Function Test (Cystatin C) | This marker only | $36.99 |
| Kidney Health Panel | 4 tests | $64.99 |
| Total Body Panel | 49 tests | $599.99 |
| Men's Superpowers Panel | 36 tests | $649.99 |
| Men's Total Body Advanced Panel | 65 tests | $999.99 |
Quest vs. Labcorp for Cystatin C: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $36.99 |
| Labcorp | Yes | $36.99 |
| BioReference (NY & NJ) | Yes | $22.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Frequently asked
What does a high Cystatin C mean?
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.
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.
Do I need a doctor's order to test my cystatin c?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Cystatin C results?
Most Cystatin C results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Cystatin C test cost?
Our Kidney Function Test (Cystatin C) starts at $36.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Cystatin C test?
Fasting is not required for the Cystatin C test. You can have your blood drawn any time of day.
Which lab will process my Cystatin C test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
Ready to test your cystatin c?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $36.99.