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  • Also Known As:
  • Ammonia Blood Test
  • NH3 Test
  • Serum Ammonia Test
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Test Quick Guide

Ammonia testing is performed to check the level of ammonia in a sample of blood. Ammonia is a chemical byproduct of digestion and other bodily processes. After being produced, ammonia is normally removed from the body by the liver and kidneys.

Ammonia testing is typically ordered to diagnose and monitor elevated ammonia levels, also known as hyperammonemia. In adults, high ammonia levels are usually the result of liver damage that causes poor liver function.

About the Test

Purpose of the test

The purpose of an ammonia test is to determine the amount of ammonia in the blood. Ammonia testing is typically performed to see if a patient has a higher than expected blood ammonia level, which is called hyperammonemia. This testing may be done for diagnosis or monitoring.

  • Diagnosis: Diagnostic tests help doctors find the cause after symptoms have developed. Doctors often perform ammonia testing in a patient with symptoms of hyperammonemia, and testing may help identify underlying conditions that affect ammonia levels, such as liver disease and certain genetic conditions.
  • Monitoring: Monitoring tests allow doctors to observe a patient’s condition over a specific period of time. Ammonia testing is used to monitor patients being treated for hyperammonemia to find out if treatment is lowering blood ammonia levels. Ammonia testing can also be prescribed to check for health complications in people with underlying conditions such as liver failure.

What does the test measure?

Ammonia testing measures the amount of ammonia in the blood. This is expressed in micrograms per deciliter of blood (μg/dL) or micromoles per liter of blood (μmol/L).

Ammonia is a waste product that is generated by normal bodily processes. It is mainly produced by bacteria in the intestines during the digestion of protein. However, ammonia also comes from other places in the body such as the kidneys, brain, and muscles.

Typically, most ammonia produced by the body is processed by the liver and converted into another waste product called urea. The kidneys then remove urea from the body in the urine.

The process through which ammonia is metabolized and converted into urea is part of the urea cycle. The urea cycle prevents ammonia from building up in the blood. If too much ammonia is in the blood, it can circulate throughout the body and eventually reach the brain. Ammonia is highly toxic to the brain. Hyperammonemia can be life-threatening and cause long-lasting effects on brain function if left untreated.

When should I get an ammonia test?

Your health care provider may order an ammonia test if you are experiencing symptoms that indicate a possible build-up of ammonia in the blood. Symptoms that suggest hyperammonemia include:

  • Confusion
  • Uncontrolled muscle movements
  • Lethargy or excessive sleepiness
  • Mood swings or changes in personality
  • Unconsciousness or coma

Health care providers also order ammonia testing in patients receiving medical care for hyperammonemia to determine whether treatment is lowering blood ammonia levels. The schedule for tests used to monitor ammonia levels depends on a range of factors including age, the cause of hyperammonemia, and the severity of the condition.

Ammonia testing is one of several tests that may be performed to help diagnose certain genetic conditions that affect the urea cycle. These conditions are relatively rare, so testing is usually only performed if symptoms or family history suggest that a patient has an inherited genetic abnormality.

A health care provider is in the best position to discuss the benefits and risks of ammonia testing and determine whether it may be appropriate in your situation.

Finding an Ammonia Test

How to get tested

Testing to evaluate ammonia levels requires a blood sample. Blood is usually drawn from a vein, and the procedure is referred to as a venous blood draw. In some situations, blood to measure ammonia levels may be drawn from an artery, which is known as an arterial blood draw.

Ammonia tests are ordered by a health professional, and the blood sample is usually drawn in a doctor’s office or hospital.

Can I take the test at home?

At-home testing to evaluate ammonia levels in the blood is not commercially available. An ammonia test must be prescribed, administered, and interpreted by a health care professional.

How much does the test cost?

The cost of testing to check ammonia levels can vary based on a range of factors. How much the test will cost can depend on your health insurance status, where the test is done, and whether other tests are ordered along with the ammonia test.

Your doctor, the facility performing the test, or your health insurance provider may be able to provide more information about testing costs including health insurance copays and deductibles.

Taking an Ammonia Test

Testing to measure ammonia levels requires a sample of blood. The sample of blood is usually drawn at a medical office or hospital.

Before the test

Pretest preparations may be necessary before an ammonia test because some substances and medications can affect your test results.

Your doctor may ask you not to smoke cigarettes or drink alcohol before your test because they can increase ammonia levels in the blood.

Your doctor may ask you to stop taking certain medications before having your blood drawn for ammonia testing. Examples of drugs that may affect ammonia levels include:

  • Barbiturates, which are drugs that may be prescribed to prevent seizures or treat anxiety, muscle spasms, or insomnia.
  • Diuretics, or water pills, which are drugs that help the body get rid of excess fluid.
  • Narcotic drugs including opioid pain medications.

Before the test, make sure to check with your doctor for specific instructions and follow them carefully in the days leading up to your blood draw.

During the test

The procedure for ammonia blood testing depends on whether the sample is being drawn from a vein or an artery.

Venous blood ammonia test

A venous blood sample is collected using a needle inserted into a vein. This method is similar to blood draws for other laboratory tests and usually takes blood from a vein on the inside of the elbow.

A health care professional will begin the procedure by cleaning the area where your blood will be drawn with an antiseptic wipe. An elastic band, called a tourniquet, may be tied above your elbow to increase the amount of the blood in the vein. A needle will be inserted, and blood will flow from the vein through the needle into a vial or test tube. Once the required amount of blood has been collected, the needle will be removed.

The procedure is usually over within a few minutes. You may feel a slight sting or pain when the needle is inserted into the vein, but this typically goes away quickly.

Arterial blood ammonia test

Most arterial blood draws use an artery in the wrist or groin area or on the inside of the elbow. Your health care provider may apply and remove pressure to test the circulation in the area where they plan to draw your blood. An antiseptic wipe will be used to clean the area. A mild anesthetic may be used to make the procedure less painful.

The health professional will palpate the artery with their fingers and then insert a pre-prepared syringe into the artery. The required blood sample will be collected, and the syringe will be removed. Pressure will be applied to the area for at least several minutes to prevent bleeding.

You may feel slightly more pain with an arterial blood draw than with a venous blood draw. Your level of discomfort may range from a slight sting to moderate pain as the needle is inserted to collect your blood, but discomfort is rarely long-lasting.

After the test

What you can expect after an ammonia test also depends on whether blood is drawn from your vein or an artery.

Venous ammonia test

After the needle is removed from your vein, pressure will be applied to the area to stop bleeding and prevent bruising. You will be given a bandage to cover the area.

You can speak with the health care professional drawing your blood about when to resume normal activities. Serious side effects are rare, but tell your doctor if you have serious or persistent pain, ongoing bleeding, or signs of an infection.

Arterial ammonia test

If the blood sample drawn for your ammonia test was taken from an artery, pressure may be applied for several minutes to prevent excessive bleeding from the collection site. Afterwards, a bandage will be applied to cover the area.

After your blood draw is complete, you may be monitored for complications. Typically, patients experience some soreness and bruising in the area where the blood was drawn. Speak with your doctor immediately if you have an increase in pain, changes to the color of your skin, or signs of infection near the puncture site.

Your health care provider can provide information about when you can return to your normal routine.

Ammonia Test Results

Receiving test results

The results of your ammonia test will usually be available to your doctor within several days. Your doctor may speak with you directly about your test results if your test was performed during a hospital stay. If your test was performed on an outpatient basis at a medical office, laboratory, or hospital, your doctor may contact you to speak with you about your test results.

If you have access to your medical record online, a test report may be uploaded to your online health portal. You may also receive a copy of your test results in the mail.

Interpreting test results

Your laboratory test report will show your measured ammonia level expressed in micrograms per deciliter of blood (μg/dL) or micromoles per liter (μmol/L).

Your test report will also show a reference range that is used to interpret your results. The reference range indicates what the laboratory considers to be an expected level of blood ammonia for a healthy person.

Elevated blood ammonia levels, also known as hyperammonemia, can suggest that the body is not effectively processing or eliminating ammonia. High ammonia levels can occur as a result of a wide range of health problems including liver failure, genetic disorders of the urea cycle, kidney disease, and a condition called Reye syndrome. When ammonia levels are too high, other tests are usually needed to help identify the exact cause.

Results of ammonia testing are interpreted based on your individual situation. This includes considering your symptoms, age, underlying medical conditions, and the results of any other tests that have been performed. Working with your doctor is the best way to understand what your test result means for your health.

Are test results accurate?

Testing to measure ammonia levels is generally regarded as accurate. However, no laboratory test is perfect, and some factors may impact the reliability of your test results.

Factors such as prolonged fist clenching and tourniquet use during your blood draw can impact the accuracy of your result. Taking certain medications, smoking cigarettes, or drinking alcohol before your test can increase blood ammonia levels. It is important to speak with your doctor about any special test preparation and closely follow any instructions in order to enhance the reliability of your test result.

Do I need follow-up tests?

An ammonia test provides information about the level of ammonia in the blood, but it can’t be used alone to diagnose an underlying health condition. If ammonia levels are too high, follow-up testing is typically needed to understand the cause.

Follow-up for an abnormal test result could include a variety of tests depending on the suspected cause of elevated ammonia levels. Your doctor may recommend additional blood work or imaging scans. Doctors may also perform tests to evaluate cognitive function.

If your test result shows an elevated blood ammonia level, you can speak with your health care provider about what other tests may be recommended.

Questions for your doctor about test results

As you review the results of your ammonia test with your doctor, it may be helpful to ask the following questions:

  • What does the result of my ammonia test mean for my health?
  • What other tests do you recommend for me at this time?
  • When do I need another ammonia test?
  • Do you recommend any treatment for me based on my test results?
  • Are there symptoms I should watch for and report to my medical team?

Related Tests

Ammonia testing in children

Ammonia testing may be performed in newborns, children, and adolescents who have symptoms that could be caused by Reye syndrome, which is a condition that can occur in children after a viral illness. Testing may also be recommended in children who have symptoms or a family history of a genetic urea cycle disorder.

Symptoms that may prompt ammonia testing in children can include:

  • Irritability
  • Seizures
  • Sleepiness or lack of energy
  • Vomiting
  • Infection

What is considered a healthy blood ammonia level varies by age. Healthy children generally have a higher blood ammonia level than is expected for a healthy adult. Your child’s doctor can best interpret ammonia test results based on your child’s age and symptoms.

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