Serum or Plasma Creatinine Concentration (Standard Method)

Why This Test Matters

Creatinine is a byproduct of muscle breakdown that your kidneys filter out of your blood. High levels may indicate kidney problems, while low levels could suggest dehydration or muscle loss. This test is a key part of evaluating kidney health, especially if you have symptoms like swelling, fatigue, or changes in urine output.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw (from a vein) or a urine sample (if part of a 24-hour collection). If you’re on a 24-hour urine test, drink plenty of fluids and avoid certain medications that could affect results. Avoid strenuous exercise or eating high-protein foods 24 hours before if instructed.

What the Results Mean

Results are typically compared to a reference range based on age, sex, and health status. Elevated creatinine levels may signal impaired kidney function, while very low levels might raise concerns about hydration or muscle metabolism. Your doctor will interpret results in the context of your overall health.

Common Causes of Abnormal Results

High creatinine levels can result from kidney disease, dehydration, severe muscle damage, or conditions like diabetes or heart failure. Low levels may occur with dehydration, low muscle mass, or certain medications. Chronic kidney disease is the most common reason for elevated creatinine.