Serum Creatinine with Glomerular Filtration Rate (GFR) Estimation

Why This Test Matters

Creatinine is a waste product from muscle metabolism that kidneys filter out of your blood. High levels or low GFR may signal kidney problems, even before symptoms appear. This test helps doctors monitor kidney function over time, especially if you have diabetes, high blood pressure, or a family history of kidney disease.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw a blood sample. If you’re on a low-protein diet or have had recent contrast dye studies, let your doctor know—these can affect results.

What the Results Mean

A creatinine test alone doesn’t diagnose kidney disease, but it’s often paired with GFR calculations (using formulas like CKD-EPI) to assess kidney function. Low levels may indicate overhydration or liver/kidney issues, while persistently high levels suggest impaired filtration.

Common Causes of Abnormal Results

Elevated creatinine can result from dehydration, kidney disease, or muscle breakdown (e.g., from injury or exercise). Low levels may occur with fluid overload, liver disease, or certain medications. GFR trends over time are more reliable for diagnosing kidney decline than single values.