Blood biochemistry: ammonia


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  • 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 .



  • Hepatic encephalopathy .
    Dogs with suspected hepatic encephalopathy should NOT be further tested using ammonia tolerance test as this may be fatal.
  • Portosystemic shunt .
    Bile acids are a better index of hepatic function.

Result data

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.

Abnormal values

Elevated levels

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.
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