Creatinine
Definition
A breakdown product of creatine phosphate in muscle. It is filtered by the kidneys and excreted in urine at relatively constant rates, making it a practical urine marker. Normal urinary creatinine is 5 to 20 mmol per litre, much higher than other body fluids.
- Source
- Breakdown product of creatine phosphate in muscle
- Normal urinary level
- 5 to 20 mmol per litre
- Excretion
- Filtered by kidneys, excreted at relatively constant rate
- Use
- Practical marker for identifying urine
Common questions
Why is creatinine's relatively constant excretion rate useful forensically?+
Because output stays fairly steady regardless of fluid intake compared to other urinary components, a creatinine concentration in the expected range supports that a stain is urine rather than a diluted or contaminated fluid.
Can creatinine testing alone confirm a stain is urine?+
No. It is one supporting indicator among several biochemical and microscopic tests used together, since creatinine also occurs at lower levels in other body fluids and a single marker is not treated as conclusive.
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