• A compound that is excreted from the body in urine. Creatinine levels are measured to monitor kidney function.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• A waste product created by muscle metabolism. Doctors sometimes test creatinine levels to examine kidney function.
  Harvard Dictionary of Health Terms
  Harvard Medical Publishing, 2011
• Nitrogen compound in muscle, blood and urine that is the end product of creatine metabolism.
  CRISP Thesaurus
  National Institutes of Health, 2006
• The breakdown product of creatine, a constituent of muscle tissue, that is excreted by the kidney and whose serum level is used to evaluate kidney function.
  NCI
  U.S. National Cancer Institute, 2021
• Creatinine is critically important in assessing renal function because it has several interesting properties. In blood, it is a marker of glomerular filtration rate; in urine, it can remove the need for 24-hour collections for many analytes or be used as a quality assurance tool to assess the accuracy of a 24-hour collection.
  Medscape
  WebMD, 2025