Serum or Plasma Creatinine Concentration

Why This Test Matters

Creatinine is a byproduct of muscle breakdown and is naturally filtered out by your kidneys. If your kidneys aren’t working well, creatinine levels can build up in your blood. This test is a key part of kidney function tests and is often used alongside other measures like blood urea nitrogen (BUN).

How the Test Works

A small blood sample is taken from your arm, usually in a doctor’s office or lab. The sample is then analyzed to measure creatinine concentration. The test can be done on serum (blood plasma after clotting) or plasma (blood plasma before clotting).

What to Expect Before the Test

There are usually no special preparations needed for this test. You may be asked to fast before the test, but this depends on the clinic or lab. Avoid strenuous activity or eating heavy meals 12 hours before if fasting is required.

Possible Results and Values

Results are typically reported in milligrams per deciliter (mg/dL) or micromoles per liter (µmol/L). While reference ranges vary by lab, higher than expected levels may signal kidney problems, while very low levels might indicate muscle disorders or other conditions.