For adults, the normal reference range for blood ammonia varies between 9.5 and 49 micrograms per deciliter. Although these are common normal ranges, these reference values can also vary among laboratories, notes WebMD. A blood test is necessary to determine the amount of ammonia in a patient's blood sample.
Children and newborns can have higher normal ranges. For example, a newborn can have a normal blood ammonia level in the range of 90 to 150 micrograms per deciliter, notes WebMD.
A doctor may recommend a blood ammonia test to diagnose different medical conditions that can cause elevated ammonia levels in the body, such as heart failure, renal failure, hypokalemia and leukemia, states the National Institutes of Health's MedlinePlus. Other factors, such as different medications and alcohol, can also elevate ammonia blood levels.
Ammonia is a waste product produced in different organs of the body, which is excreted in urine.