Green (heparin) top, lavender (EDTA) top or Red top tube.
Fill tube completely with venous blood.
Additional instructions:
Ammonia is a waste product of cellular protein metabolism and is also produced by bacteria in the intestine. The liver converts ammonia to urea which is then renally excreted into the urine.
If ammonia metabolism is inadequate toxic effects will occur affecting the central nervous system.
The clinical utility of this test is:
In some liver diseases, the hepatocytes fail to adequately metabolize ammonia to urea. The result will be an increased ammonia level. Depending on the nature of the liver disease; the ammonia level may or may not indicate the severity of the disease.
Newborns commonly have slightly higher levels of blood ammonia. These levels are transient and usually cause no symptoms. In the newborn, blood ammonia test is performed when symptoms such as irritability, vomiting, lethargy and seizures appear during the first few days.
Clinical signs of hyperammonemia are seen at blood ammonia concentrations > 60 mmol/L. These signs include:
Note: Normal ammonia levels do not completely exclude encephalopathy being hepatic in cause, in the patient with significant liver disease.
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
The blood ammonia level varies with age.
| Conv. units (µg/dL) | SI units (µmol/L) | |
|---|---|---|
| Newborn | 36-340 | 21-200 |
| 1-12 mo | 31-128 | 18-75 |
| 1-12 yr | 31-80 | 18-68 |
| Adult | 19-60 | 11-35 |
An increased blood ammonia level (hyperammonemia) is seen in the following conditions:
Drugs that cause increase in blood ammonia levels include:
Decreased blood ammonia may occur in the following conditions:
Drugs/organisms that cause a decrease in blood ammonia level include: