Serum or Plasma Creatinine Concentration (Mass Concentration)

Why This Test Matters: Kidney Health

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 overhydration or muscle wasting. This test is often used alongside other measures to evaluate kidney health, especially if you have symptoms like swelling, fatigue, or changes in urine output.

When You Might Need This Test

Your doctor may order this test if you have symptoms of kidney problems, such as swelling in your legs or feet, frequent urination at night, or unexplained fatigue. It’s also commonly checked during routine health evaluations, especially if you have conditions like diabetes or high blood pressure that increase kidney risk.

What to Expect Before the Test

You’ll typically have a small needle inserted into your arm or vein to draw blood. No special preparation is usually needed, but your doctor may advise avoiding certain medications or foods for a few days before the test if directed.

What the Results Mean

Results are compared to a reference range based on your age, sex, and overall health. While creatinine levels alone don’t diagnose kidney disease, they’re part of a larger picture that includes other tests like blood pressure and urine tests. Your doctor will discuss the results in the context of your overall health.