- Primarily absorbed from GI tract, especially colon. Lower levels from muscle metabolism.
- Increased levels may be seen with impaired liver function or portosystemic shunt.
- Used in investigation of hepatic encephalopathy .
Normal (reference) values
Check own laboratory normal values, those quoted below are for guidance only.
- Fasting level: <120 umol/l.
- <80 ug/ml.
- Conversion factor: ug/dl x 0.5872 → umol/l.
Errors and Artifacts
- Non-EDTA anticoagulants may contain ammonium, giving falsely high results.
- Samples tested more than 2 h after collection may have elevated levels due to breakdown of urea.