Creatinine is a waste product formed from the breakdown of muscle creatine.

It is filtered almost entirely by the kidneys, making it a reliable marker of renal function.

Clinical uses include:

Diagnosing acute or chronic kidney disease.

Monitoring patients with diabetes, hypertension, or cardiovascular disease.

Assessing kidney function before prescribing nephrotoxic drugs.

Calculating estimated glomerular filtration rate (eGFR) for a more complete picture of renal health.

The test is performed using a blood sample.

Analyte: Serum creatinine concentration.

Normal Range: ~0.6 – 1.3 mg/dL (varies slightly by lab, sex, and muscle mass).

Abnormal Findings:

High creatinine: Suggests impaired kidney function, dehydration, or muscle injury.

Low creatinine: May occur in reduced muscle mass, malnutrition, or certain liver diseases.

Clinical Use:

Provides a key measure of renal filtration efficiency.

Helps differentiate acute vs. chronic kidney impairment.

Guides treatment and monitoring in renal and systemic conditions.