Serum or Plasma Creatinine Concentration (Standard Method)

Why This Test Matters

Creatinine is a byproduct of muscle breakdown and is normally filtered out of your blood by your kidneys. High levels can indicate poor kidney function, while low levels may suggest dehydration or other conditions. This test is often used alongside other kidney function tests to diagnose or monitor kidney disease.

What to Expect Before the Test

You may be asked to fast for a few hours before the test, but this is not always required. If you’re having a blood test, a healthcare provider will draw blood from a vein in your arm. For a urine test, you’ll collect a sample in a clean container. Drink plenty of water the day before if you’re having a urine test to ensure a representative sample.

How the Test Works

Blood tests measure creatinine concentration using a method that detects its presence in your serum or plasma. Urine tests measure creatinine content in your urine, often over a 24-hour period, to assess kidney function more precisely.

What the Results Mean

Results are compared to standard reference ranges, which can vary slightly by lab. High creatinine levels may signal kidney issues, while very low levels might indicate dehydration or other health concerns. Your doctor will interpret results in the context of your overall health and other tests.