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Samples required

EDTA blood (purple cap/ yellow cap ring, 4 mL tube). Smaller tubes are available for paediatric samples.

Immediate transport to laboratory on ice. Avoid contamination of sample. Avoid haemolysis.

Do not send via pneumatic tube (pod) system.

Outside routine hours, please bleep biochemistry laboratory scientist.

Test indications


Factors affecting test performance/ results

Contamination with erythrocyte contents will elevate results, because the ammonia concentration in erythrocytes is higher than in normal plasma. The degree of interference may be variable depending on the content of analyte in the lysed erythrocytes. Potentially affected results will be blocked.

Cefoxitin and Intralipid cause artificially high and low ammonia results respectively at the therapeutic drug level.

Physiological plasma concentrations of sulfasalazine and sulfapyridine may lead to false results.

Temozolomide at therapeutic concentrations may lead to erroneous results.

In very rare cases, gammopathy, in particular type IgM (Waldenström’s macroglobulinemia), may cause unreliable results.

Results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings.

Reference range

male: 16 - 60 µmol/L
female: 11 - 51 µmol/L
Source: Roche Cobas® Ammonia kit insert, 05-2014, V9.0

Turnaround time

1 hour


Biochemistry (Automation)