Ammonium ion

Answer 1

Definition

Ammonium ion test measures the amount of ammonium ions in a blood sample.

Alternative Names

NH4+ test; Ammonia nitrogen level

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

Fast for 8 - 12 hours. The health care provider may advise you to withhold drugs that may affect test results.

Drugs that can interfere with the test include thiazide or loop diuretics, barbiturates, acetazolamide, neomycin, and oral kanamycin. Consult the health care provider before this test if you are taking any of these medications.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test may be performed when a condition that may cause toxic accumulation of ammonia is present or suspected. It is most commonly used to diagnose and monitor hepatic encephalopathy, a severe liver disease.

Ammonia (NH4+) is produced by cells throughout the body, especially the intestines, liver, and kidneys. Most of the ammonia produced in the body is used by the liver in the production of urea. Urea is also a waste product but is much less toxic than ammonia.

Ammonia is especially toxic to the brain and can cause confusion, lethargy, and sometimes coma.

Normal Values

The normal range is 15 - 45 micrograms per deciliter (mcg/dL).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Conditions that can increase ammonia levels include:

• Liver failure
• Severe congestive heart failure
• Erythroblastosis fetalis
• Gastrointestinal (GI) bleeding - usually in the upper GI tract
• Genetic diseases of the urea cycle
• Leukemia
• Pericarditis
• Reye syndrome
• Certain drugs

What the risks are

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Patients with liver disease may have clotting problems. After the venipuncture, pressure should be applied to the puncture site for several minutes to ensure that bleeding has stopped.

References

Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 150.

Answer 2

Definition

The ammonium - blood test measures the amount of ammonia in a blood sample.

Alternative Names

Ammonia level

How the test is performed

A blood sample is needed. For information on how this is done, see: Venipuncture

How to prepare for the test

Fast for 8 - 12 hours. The health care provider may recommend that you stop taking drugs that may affect your test results.

Drugs that can falsely raise the blood amminia level include alcohol, acetazolamide, narcotics, and valproic acid. A high-protein diet can also raise the blood ammonia level. Talk to your health care provider before this test if you are taking any of these medications.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test may be done if you have or are thought to have a condition that may cause a toxic buildup of ammonia. It is most commonly used to diagnose and monitor hepatic encephalopathy, a severe liver disease.

Ammonia (NH3) is produced by cells throughout the body, especially the intestines, liver, and kidneys. Most of the ammonia produced in the body is used by the liver to produce urea. Urea is also a waste product, but it is much less toxic than ammonia.

Ammonia is especially toxic to the brain. It can cause confusion, lethargy, and sometimes coma.

Normal Values

The normal range is 15 - 45 micrograms per deciliter (mcg/dL).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

What abnormal results mean

Conditions that can increase ammonia levels include:

• Congestive heart failure
• Gastrointestinal (GI) bleeding - usually in the upper GI tract
• Genetic diseases of the urea cycle
• Hyperthermia (high body temperature)
• Leukemia
• Liver failure
• Muscle exertion

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Patients with liver disease may have clotting problems. After the venipuncture, pressure should be applied to the puncture site for several minutes to ensure that bleeding has stopped.

References

Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 150.

Nevah MI, Fallon MB. Hepatic encephalopathy, hepatorenal syndrome, hepatopulmonary syndrome, and systemic complications of liver disease. In: Feldman L, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Diseases. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 92.

Reviewed By

Review Date: 02/21/2011

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.