Ammonia Test: When Is It Ordered & What Does It Detect?

What Is an Ammonia Test?

An ammonia test is a blood test that measures the amount of ammonia, a nitrogen waste product, circulating in your bloodstream. Ammonia (NH3) is normally produced by bacteria in the intestines during the digestion of protein. Your liver typically converts this toxic substance into urea, which is then removed from the body by the kidneys. The ammonia blood test helps doctors assess if your ammonia levels are within a normal range. Abnormal ammonia levels can indicate a problem with the liver or kidneys, or an underlying metabolic disorder that disrupts the urea cycle. The use of an ammonia test is therefore crucial to identify these potential health issues.

Why Is the Ammonia Test Done?

Your doctor may order an ammonia test to check for elevated blood ammonia, a condition known as hyperammonemia. Excess ammonia can be toxic, especially to the brain, leading to serious neurological symptoms. The ammonia levels test helps diagnose the cause behind symptoms like confusion, lethargy, or even coma. It's also commonly done if you have unexplained changes in mental status or consciousness; signs of liver damage or hepatic encephalopathy; kidney disease that may impair ammonia excretion; or, a family history of rare inherited metabolic conditions like urea cycle disorders.

Conditions That Require Ammonia Testing

Several health conditions may require an ammonia blood test procedure for diagnosis or monitoring. These include:

• Liver diseases like cirrhosis or hepatic encephalopathy, where a damaged liver cannot properly remove ammonia from the blood
• Kidney failure, which can impair ammonia excretion
• Inherited metabolic disorders such as urea cycle defects that cause ammonia buildup
• Reye's syndrome, a rare but serious condition that can cause brain and liver damage in children

Doctors often order ammonia testing along with other liver function tests for people with symptoms suggestive of these conditions. The ammonia test procedure is vital for both initial diagnosis and tracking treatment response over time.

Symptoms That May Lead to Ordering the Test

Elevated blood ammonia can cause neurological symptoms as the brain is very sensitive to its toxic effects. Hallmark signs that often prompt an ammonia test include confusion, disorientation, altered mental status; excessive sleepiness, lethargy, fatigue; personality or behavioural changes; slurred speech, impaired verbal response; seizures, tremors, muscle twitching; nausea, vomiting, loss of appetite; or, unusual infant behaviour such as irritability, poor feeding, rapid breathing.

These symptoms are more concerning if you have a history of liver or kidney problems. In such cases, your doctor will likely order an ammonia levels test to check for hyperammonemia as a potential cause or complication.

How the Ammonia Test Works

For the ammonia test procedure, a healthcare professional will draw a blood sample from a vein in your arm using a needle and collect it in a tube. Ammonia levels can fluctuate significantly after the blood is drawn. Therefore, the sample is handled carefully to prevent any changes due to temperature or delayed processing that could affect the accuracy of results.

The blood sample is usually placed on ice immediately and sent to the lab for prompt analysis. The ammonia blood test measures the concentration of ammonia in the blood, reported as micrograms per deciliter (mcg/dL) or micromoles per liter (μmol/L).

How to Prepare for the Ammonia Test

To ensure reliable ammonia blood test results, some advance preparation may be needed:

• Fast for 8-12 hours before the test, as recently consumed protein can increase blood ammonia.
• Avoid strenuous exercise prior to the test.
• Inform your doctor about any medications or supplements you take, as some may affect ammonia levels.
• For infants and young children, the doctor will provide specific feeding instructions.

Your healthcare provider will give you detailed preparation guidelines to follow. Adhering to these instructions is important for obtaining accurate results.

What to Expect During the Procedure

The ammonia test involves a standard blood draw, a quick procedure that typically takes only a few minutes.

• You may feel a slight pinch or sting when the needle is inserted
• After the needle is withdrawn, the puncture site will be covered with a small bandage to prevent bleeding.
• Some people may feel lightheaded, dizzy, or nauseated during or after the blood draw.
• You may have some residual pain or bruising at the needle site for a day or two, which can be relieved by applying ice or pressure.

Interpreting Ammonia Test Results

The interpretation of ammonia test results involves comparing the measured blood ammonia level to the reference range provided by the laboratory. A normal ammonia level for a healthy adult typically falls between 15 to 45 mcg/dL (11 to 32 μmol/L). However, the reference range may vary slightly among different labs.

Infants and young children normally have slightly higher blood ammonia levels than adults. The normal range for newborns is 90-150 mcg/dL (64-107 μmol/L), gradually decreasing over the first few months of life.

Your doctor will consider your ammonia level alongside your age, health history, and presenting symptoms to determine if the result is concerning. A single elevated ammonia level needs to be confirmed with repeat testing.

Normal vs. Abnormal Ammonia Levels

If your ammonia test result falls within the lab's reference range, it is considered normal. A normal ammonia level suggests that your liver and kidneys are effectively processing and eliminating ammonia from your body.

An abnormal result, either higher or lower than the expected range for your age, may indicate an underlying problem. Elevated ammonia levels are much more common and clinically significant than low levels.

However, it's essential to remember that a single abnormal ammonia test does not necessarily mean you have a serious health issue. Your doctor will interpret the result in the context of your symptoms, medical history, and other diagnostic findings to determine if further evaluation or treatment is needed.

What High Ammonia Levels Might Indicate

If your ammonia blood test shows a high result, it could mean several things. Some potential causes of elevated ammonia include cirrhosis or severe liver disease; hepatic encephalopathy, a brain disorder caused by liver failure; kidney failure or severe kidney disease; or, inherited metabolic disorders like urea cycle defects.

Less commonly, certain medications, gastrointestinal bleeding, or urinary tract infections can also raise blood ammonia levels. Your doctor will consider your medical history, perform a physical exam, and possibly order imaging scans or additional liver function tests to pinpoint the underlying cause.

Also Read: Liver Function Tests: What You Need to Know

What Low Ammonia Levels Might Mean

While less common, abnormally low blood ammonia levels can sometimes occur due to:

• Impaired ammonia production in the intestines, often related to prolonged fasting or malnutrition
• Overhydration or excessive fluid intake, which can dilute blood ammonia
• Pregnancy, where ammonia levels naturally decrease by up to 50% compared to non-pregnant women

In most cases, low ammonia levels do not indicate a serious health concern and may not require specific treatment. However, your doctor will consider your overall health status and symptoms to determine if further evaluation is warranted.

Risks and Limitations of the Test

The ammonia blood test uses are several and it is considered a safe and low-risk procedure. However, as with any blood draw, there is a small chance of bruising or pain at the needle site; dizziness or fainting; or, infection, in very rare cases.

More often, the greater risk is an inaccurate result. Ammonia is very sensitive to changes in temperature and can be lost from the blood sample if it is not handled properly. Clenching your fist during the draw or waiting too long to process the sample can cause falsely elevated levels.

When to Repeat or Follow Up with Additional Tests

Your healthcare provider may recommend repeating your ammonia levels test if the initial test was possibly mishandled, your levels are only mildly elevated, or you have concerning symptoms despite a normal first result.

For abnormally high ammonia levels, your doctor will likely order follow-up tests to check your liver and kidney function. Additional blood and urine tests, imaging scans, or sometimes genetic tests can help determine the root cause of high ammonia. Prompt diagnosis is key to preventing complications.

Final Thoughts

The ammonia test uses include diagnosing liver dysfunction and evaluating unexplained confusion or coma. It's a crucial tool for early detection of metabolic or hepatic disorders. If recommended by your doctor, don’t delay testing. At Metropolis Healthcare, we offer accurate diagnostics with home sample collection. The ammonia test price is affordable and varies by location. Book your test today for timely results and informed healthcare decisions.

FAQs

What does a high ammonia level mean?

A high ammonia level in the blood may indicate liver dysfunction, such as cirrhosis or hepatitis, which prevents the liver from properly processing ammonia. It can also be linked to kidney failure, genetic disorders, or certain infections, especially in children.

Is fasting required before the test?

Fasting is not always required, but your healthcare provider may advise it depending on your symptoms or medical history. Following specific instructions can help ensure accurate test results.

Can medications affect ammonia test results?

Yes, some medications—such as diuretics, valproic acid, or chemotherapy drugs—can influence ammonia levels. Always inform your doctor about any prescriptions or supplements you are taking before the test.

How quickly are ammonia test results available?

Results are typically available within a few hours to a day, depending on the laboratory. In emergency settings, rapid testing may be performed for immediate diagnosis.

Is the ammonia test painful?

The test involves a standard blood draw, which may cause mild discomfort or a slight pinch. Most people experience minimal pain, and any soreness usually resolves quickly.

Can liver disease cause high ammonia levels?

Yes, liver disease is one of the primary causes of elevated ammonia levels, as the liver is responsible for converting ammonia into urea for excretion. Impaired liver function can lead to ammonia buildup in the bloodstream.

Read: Liver Diseases: Their Types, Symptoms and More

When should a child have an ammonia test?

A child may need an ammonia test if they show signs of confusion, vomiting, lethargy, or seizures, especially when metabolic or genetic disorders are suspected.

What follow-up tests are usually recommended after an abnormal result?

Follow-up tests may include liver function tests, kidney function tests, or imaging studies to identify the root cause of elevated ammonia levels.