Ammonia Test – Purpose, Normal Range, and High Ammonia Levels Explained

Overview

The Ammonia Test is a blood test that measures the level of ammonia (NH₃) in your body.
Ammonia is a waste product formed when the body breaks down protein. Normally, the liver converts ammonia into urea, which is then safely eliminated from the body through urine.

However, if the liver is not functioning properly, ammonia can build up in the bloodstream.
This can become toxic, especially to the brain, and cause confusion, drowsiness, and even coma.

Doctors usually order an ammonia test to:

• Check liver function
• Diagnose or monitor hepatic encephalopathy
• Investigate unexplained confusion, coma, or behavioral changes

What is Ammonia?

Ammonia (NH₃) is a chemical waste product produced naturally during protein metabolism.
It is a toxic compound and must be quickly processed by the liver to prevent it from harming the body.

In healthy individuals:

• The liver converts ammonia → urea
• Urea travels through the blood → kidneys
• Kidneys remove urea → urine

When this process fails, ammonia accumulates, which can disturb brain function — a condition known as hyperammonemia.

Where is Ammonia Produced in the Body?

Ammonia is produced in different parts of the body during the normal breakdown of proteins.

Main sources include:

• Intestines: Bacteria in the gut release ammonia while digesting proteins.
• Muscles: During exercise or protein breakdown, small amounts of ammonia are produced.
• Kidneys: Help regulate ammonia as part of maintaining acid–base balance.

Once formed, ammonia enters the bloodstream and travels to the liver, where it is converted into urea. The urea then passes to the kidneys for excretion through urine.

Main Functions and Importance

• Ammonia itself has no beneficial function.
  It is simply a waste product that needs to be detoxified.
• The liver converts ammonia to urea through the urea cycle.
• If the liver is damaged or not functioning properly, ammonia accumulates in the blood, which can be toxic to the brain.
• Measuring ammonia levels helps assess liver function and detect metabolic or neurological problems.

Causes of Low Ammonia Levels

Low ammonia levels are uncommon and usually not harmful.
They may be seen in:

• Low protein intake
• Malnutrition
• Certain medications
• After recovery from liver disease

Since ammonia is a waste product, having low levels is normal and not a health concern.

Symptoms of Low Ammonia Levels

Low ammonia levels do not cause any symptoms and are generally considered clinically insignificant.

Causes of High Ammonia Levels (Hyperammonemia)

High ammonia levels occur when the body produces too much ammonia or fails to remove it efficiently due to liver or metabolic problems.

Common causes include:

• Liver failure or cirrhosis (liver cannot convert ammonia to urea)
• Hepatic encephalopathy (brain dysfunction due to high ammonia)
• Reye’s syndrome (a rare but serious condition in children)
• Genetic urea cycle disorders (inherited enzyme deficiencies)
• Gastrointestinal bleeding (digested blood increases protein load)
• Severe infections or trauma
• Kidney failure (reduced excretion of ammonia)
• Certain medications (e.g., valproic acid, diuretics)
• High-protein diet or excessive protein breakdown

Symptoms of High Ammonia Levels

When ammonia levels rise, the brain is affected first.
This condition, known as hepatic encephalopathy, may cause the following symptoms:

In Adults:

• Confusion, forgetfulness
• Irritability or behavioral changes
• Difficulty concentrating
• Excessive sleepiness or drowsiness
• Slurred speech
• Tremors or shaking hands
• Nausea and vomiting
• Seizures
• Coma (in severe cases)

In Infants or Children:

• Poor feeding or refusal to eat
• Vomiting
• Unusual sleepiness or lethargy
• Low body temperature
• Seizures
• Developmental delays (in inherited urea cycle disorders)

If untreated, high ammonia levels can be life-threatening, so urgent medical evaluation is needed.

Reference Ranges (Normal Values)

⚠️ Levels above 60 µg/dL may suggest hepatic encephalopathy, urea cycle disorder, or severe liver failure.

Always compare your result with the reference range given by your testing laboratory.

Sample Type and Handling

The Ammonia Test is performed using a blood sample, usually from a vein in the arm.

Because ammonia levels can change quickly, sample handling is extremely sensitive:

• Blood must be collected in a heparinized or EDTA tube.
• The sample must be kept on ice immediately after collection.
• It should be tested within 15–30 minutes.
• Avoid using a tight tourniquet or clenching your fist, as it may falsely raise ammonia levels.

Proper collection is essential for accurate results.

Why the Ammonia Test is Important

Doctors recommend the ammonia test to:

• Check liver function and detect liver failure.
• Diagnose hepatic encephalopathy (a complication of advanced liver disease).
• Evaluate unexplained confusion, coma, or neurological symptoms.
• Monitor metabolic disorders or urea cycle enzyme deficiencies in infants and children.

It is often ordered along with Liver Function Tests (LFTs) for a complete liver health assessment.

Test Preparation

To ensure accurate results:

• Fasting may be required (as advised by your doctor).
• Avoid smoking and strenuous exercise before the test.
• Inform your doctor about medications you are taking (especially diuretics or valproic acid).
• Avoid prolonged use of a tourniquet during blood draw.

Treatment for High Ammonia Levels

Treatment depends on the underlying cause:

• For liver disease: Reduce protein intake and use medications like lactulose or rifaximin to lower ammonia.
• For urea cycle disorders: Special low-protein diet and medications to remove ammonia.
• For medication-induced cases: The offending drug is stopped or replaced.

Early diagnosis and treatment can prevent brain damage or coma.

When to Consult a Doctor

Consult your doctor if you notice:

• Confusion or unusual behavior
• Sudden drowsiness or loss of alertness
• Slurred speech or tremors
• Yellowing of the skin (jaundice)
• Persistent vomiting or abdominal pain

If you have chronic liver disease or cirrhosis, periodic ammonia testing may be advised to monitor your condition.

Important Word Explanations

• Ammonia (NH₃): A toxic waste product from protein breakdown.
• Urea: A harmless compound formed when ammonia is converted by the liver.
• Hepatic encephalopathy: Brain dysfunction caused by high ammonia due to liver failure.
• Hyperammonemia: Abnormally high ammonia levels in the blood.
• Cirrhosis: Long-term scarring of the liver.

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