Creatinine

Background

Creatinine is formed from creatine following its conversion from phosphocreatine during muscle contraction. Since creatinine is a product of muscle activity and the muscle mass of an individual tends to remain constant, creatinine production varies very little from day to day.

Both creatinine and creatine are filtered by the glomerulus, but while creatine is reabsorbed by the tubules, creatinine is excreted in the urine. As creatinine production and therefore excretion are normally constant it follows that creatinine production and excretion are of value in monitoring renal disease and renal dialysis.

In the absence of renal disease creatinine measurements are also of value as a base for measuring other metabolites in urine.

Reference ranges

Serum
Adult: 50 – 120 umol/L
Urine
Male: 7100 – 15900 umol/24hrs
Female: 5200 – 14100 umol/24hrs

Specimen requirements

Sample type:

• Serum: Serum or Lithium Heparin Plasma.
• Urine: Plain 24 hour or random urine, no preservative.

Sample identification:

• Three patient identifiers from
  • Name
  • D.O.B.
  • Address
  • N.H.S. number
  • Unit Number
  should match on the specimen and request form. This check may be performed prior to centrifugation by the Central Sort department.

Turnaround time

2 hours