Factors that may contribute to a falsely elevated blood ammonia level:
(1) recent smoking
(2) ammonium ions in the anticoagulant
(3) citrate, oxalate or fluoride used as anticoagulant
(4) failure to keep the blood sample on ice immediately after collection
(5) failure to quickly separate plasma from the red blood cells using a refrigerated centrifuge
(6) failure to analyze within 20 minutes of collection or to freeze until analyzed
(7) hemolysis
(8) use of venous blood rather than arterial, especially with prolonged tourniquet times or repeated fist clenchings
(9) unreliable assay
(10) recent exercise
(11) recent blood transfusion
(12) high protein diet or hyperalimentation
(13) ammonia in the atmosphere
(14) contamination of the specimen with sweat
Drugs that may elevate the blood ammonia level:
(1) ammonium acetate or other salts
(2) asparaginase
(3) barbiturates
(4) diuretics
(5) narcotics
(6) valproic acid
