Creatinine

Overview

Creatinine measures a waste product from creatine phosphate breakdown in muscle metabolism, filtered by the glomeruli with minimal tubular reabsorption. Serum levels reflect glomerular filtration rate (GFR), serving as an endogenous marker of kidney function. Elevated levels indicate impaired renal clearance from acute or chronic kidney disease, while low levels may reflect reduced muscle mass. It is clinically useful for estimating GFR (eGFR), diagnosing and staging chronic kidney disease, and monitoring renal function changes.kidney+2

Clinical Use Cases

  • Diagnosing acute kidney injury and chronic kidney disease.
  • Monitoring progression of known kidney disease.
  • Assessing medication safety (nephrotoxic drugs).
  • Evaluating kidney transplant function.mayoclinic+1

Specimen Types

Measurement Methods

  • Jaffe kinetic alkaline picrate assay (IDMS-traceable).
  • Enzymatic creatinine amidohydrolase method.
  • HPLC or LC-MS/MS (reference method).[kidney</a >]​

Test Preparation and Influencing Factors

  • No fasting required.
  • High muscle mass, diet (cooked meat), or cephalosporins elevate levels.
  • Low muscle mass (age, malnutrition, amputation) lowers levels.
  • Race, sex, age used in eGFR calculations; acute changes lag GFR by 24-48 hours.medicalnewstoday+1

Synonyms

  • Serum creatinine.
  • SCr.
  • Plasma creatinine.

Further Reading

  • Creatinine Test: MedlinePlus Medical Test; MedlinePlus;