Pathology tests database

Sample and container requirements

EDTA Plasma

Minimum volume required

Special requirements

Ammonia concentrations increase rapidly in blood after venepuncture. Please note time of sample collection on the form and transport sample immediately to the laboratory. Sample should be received within 30 minutes of collection. If possible transport samples on ice.

Patient preparation

A free-flowing venous blood sample should be collected into EDTA tube. Drawing blood through a small indwelling catheter can cause haemolysis and hence falsely high ammonia.

Sample viability

Turnaround time

This assay is run throughout the day and night. The in-lab turnaround time is normally less than 24 hours. The test can be ordered as an urgent request.

Reference range

Neonates (<4 weeks): <100 µmol/L 4 weeks – 16 years: <50 µmol/L Sick or premature babies: <150 µmol/L (Source: Pathology Harmony Recommendations) Adults: 18 – 72 µmol/L (Source: Abbott Diagnostics)

Clinical guidance

Ammonia measurement is useful in evaluating patients with advanced liver disease, investigating and monitoring treatment for inborn errors of metabolism, and in coma or encephalitis associated with liver disease. Please refer to LabTestsOnlineUK to learn more about ammonia. https://labtestsonline.org.uk/tests/ammonia

Notes

It is recommended that any high ammonia values are confirmed using fresh venous blood, collected onto ice and received within the laboratory within 30 minutes of collection. Discrepancies between capillary and venous samples can occur, venous blood is the preferred specimen. The concentration of ammonia is significantly increased by haemolysis.