Serum or Plasma Creatinine Concentration (Substance Concentration)

Why This Test Matters

Your kidneys normally filter waste products, including creatinine, from your blood. High levels may indicate impaired kidney function, while very low levels could suggest muscle breakdown or other conditions. This test is often used alongside other measures to monitor kidney health, especially in people with diabetes, high blood pressure, or a history of kidney disease.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small needle inserted into a vein (usually in your arm) to draw blood. If you’re having a 24-hour urine test for creatinine clearance, you’ll need to collect all urine over 24 hours, starting after your first morning urine. Drink plenty of fluids unless instructed otherwise.

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). While reference ranges vary by lab, higher than expected levels may signal kidney problems, while lower levels may need further investigation. Your healthcare provider will interpret results in the context of your overall health.

Common Causes of Abnormal Results

High creatinine levels can occur due to kidney disease, dehydration, severe muscle damage, or conditions that reduce blood flow to the kidneys. Low levels may be seen in muscle disorders, liver disease, or certain medications. Other factors, like recent exercise or high protein intake, can temporarily affect results.