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: An ammonia test is often done if a patient has symptoms of hyperammonemia. Testing may help identify underlying conditions that affect ammonia levels, such as certain genetic conditions (urea cycle disorders) , liver disease (cirrhosis or hepatitis), and hepatic encephalopathy.
- Monitoring: Patients being treated for hyperammonemia are given an ammonia test to monitor treatment and find out if it’s lowering blood ammonia levels. This test can also help monitor potential 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). Normal values may vary from laboratory to laboratory, but generally fall within 15-45 µ/dL (11 to 32 µmol/L). Understanding what ammonia is and how it’s processed in the body can help explain why this test is useful for identifying underlying health issues.
Ammonia is a waste product that is generated by normal bodily processes, mainly 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, thus preventing ammonia from building up in the blood. In chronic kidney disease, the kidney can not adequately process large amounts of ammonia
If too much ammonia is in the blood, it can circulate throughout the body and is found in liver failure as well as toxicity of skeletal muscles. Elevated ammonia levels can be highly toxic to the brain resulting in hyperammonemia, a life-threatening situation that can cause long-lasting effects on brain function if left untreated. Genetic conditions that involve elevated ammonia levels are generally a result of Urea Cycle Disorders (UCDs), as well as other disorders that interfere with the removal of ammonia. Abnormal ammonia levels are also found in such disorders as”
- Gastrointestinal (GI) bleeding
- Hyperthermia
- Kidney or liver disease
- Low potassium levels
- Reye syndrome (a condition of unknown cause but can follow a viral infection)
- Salicylate poisoning (NSAID)
- Severe muscle exertion
- Urinary tract reconstruction
- Urinary tract infection (Proteus mirabilis)
- High protein diet
When should I get an ammonia test?
Your health care provider may order an ammonia test if you’re experiencing symptoms that indicate a possible build-up of ammonia in the blood, especially when a liver condition or metabolic disorder is suspected.
In adults, symptoms of elevated ammonia levels often affect the brain and nervous system and may include:
- Confusion or difficulty concentrating
- Excessive sleepiness or fatigue
- Irritability or changes in behavior
- Headaches
- Nausea or vomiting
- Poor coordination or trouble walking
- Slurred speech
- Tremors, seizures
- Loss of consciousness in severe cases, coma, brain swelling
Ammonia testing may also be used in infants and children when symptoms appear suddenly or early in life. These may include:
- Extreme sleepiness or low energy
- Poor feeding or refusal to eat
- Vomiting
- Rapid or labored breathing
- Irritability or behavioral changes
- Delayed development or loss of previously learned skills
- Hypothermia (decreased body temperature) or hypotonia (floppiness)
Because many of these symptoms can develop gradually or be mistaken for other conditions, testing is often used alongside other evaluations to help identify the underlying cause – such as liver disease or complications like hepatic encephalopathy.
Ammonia testing is one of several diagnostic tools that may also be used to help diagnose certain genetic disorders affecting the urea cycle. These conditions are relatively rare, so testing is often 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
An ammonia test is usually done in a hospital, doctor’s office, or lab. In many cases, a doctor orders this test when symptoms appear suddenly or are severe. You may have your blood drawn in a hospital or outpatient lab, depending on your situation.
If your symptoms are less urgent, you may be able to request testing through a health care provider or a direct-access lab service. This typically involves scheduling a blood draw at a local lab.
Can I take the test at home?
At-home ammonia tests are not generally available. While you may be able to order your own test, the sample must still be collected at a lab, hospital, or medical office, and results should be interpreted with a clinician.
How much does the test cost?
Ammonia testing can vary in price based on a range of factors. It will depend on your health insurance status, where the test is done, and whether other tests are ordered.
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 blood draw performed at a lab, medical office, or hospital. Here’s what you can expect throughout the process.
Before the test
There are several factors that can influence your body’s ammonia levels, so you may be asked to avoid certain activities or substances before an ammonia test. Before the test, follow any instructions from your provider. To ensure accurate results, you may be advised to:
- Avoid smoking or alcohol before the test
- Avoid strenuous exercise for several hours beforehand
- Avoid taking certain medications or supplements (e.g., barbiturates, diuretics, narcotics, valproic acid)
During the test
Ammonia testing is usually done with a blood sample taken from a vein in your arm. A health care provider will clean the area and insert a small needle to collect blood into a vial or tube. The process typically takes only a few minutes.
You may be asked to relax your hand and avoid clenching your fist during the blood draw. This is because muscle activity can temporarily increase ammonia levels.
Because ammonia levels can change quickly after the sample is collected, the blood sample is handled promptly and may be placed on ice to be processed soon after collection.
After the test
After a blood draw, you can usually return to your normal activities right away. You may have mild soreness or bruising at the site where the needle was inserted, but this typically goes away quickly.
There are no special restrictions after most ammonia tests. However, your provider may give you additional instructions depending on your symptoms or overall health.
If you undergo an arterial blood draw, 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.