From the Guidelines
The normal range for ammonia levels in the blood is typically considered to be ≤35 µmol/l (<60 µg/dl). This value is based on the most recent and highest quality study available, which emphasizes the importance of monitoring ammonia levels to prevent neurological impairment and cerebral edema 1.
Key Points to Consider
- Ammonia levels are crucial in diagnosing and managing hyperammonaemia, which can result from various conditions including liver dysfunction, urea cycle disorders, and organic acidemias.
- Elevated ammonia levels can lead to severe neurological symptoms, including confusion, lethargy, and coma, highlighting the need for prompt identification and treatment.
- The normal range for ammonia may vary slightly depending on the laboratory and testing method used, but levels above 35 µmol/l are generally considered abnormal and warrant further investigation.
Clinical Implications
- Monitoring ammonia levels is essential in patients with liver disease, as elevated levels can indicate hepatic encephalopathy and predict further decompensation of cirrhosis 1.
- In pediatric patients, hyperammonaemia can be particularly challenging to manage due to non-specific clinical symptoms and age-specific etiologies, emphasizing the need for prompt and effective treatment strategies 1.
Treatment and Management
- Treatment of hyperammonaemia focuses on addressing the underlying cause and may include medications to reduce ammonia production in the intestines, such as lactulose or rifaximin.
- In severe cases, kidney replacement therapy may be necessary to rapidly reduce ammonia levels and prevent neurological damage 1.
From the Research
Normal Range for Ammonia Levels
The normal range for ammonia levels in humans is between 11 and 50 µM, as stated in the study 2. Another study 3 mentions that the blood concentration of ammonia is maintained at a concentration of only about 30 µM.
Comparison of Studies
- The study 2 provides a range of 11-50 µM for normal ammonia levels.
- The study 3 mentions a specific value of 30 µM for normal ammonia levels.
- The study 4 reports a median blood ammonia level of 10 μmol L(-1) for healthy participants, which is within the normal range.
Abnormal Ammonia Levels
Abnormal ammonia levels are associated with various pathological conditions, such as liver and kidney dysfunction, Reye's syndrome, and urea cycle disorders, as mentioned in the study 2. Elevated blood ammonia levels can reach up to 1 mM in some cases.
Clinical Utility of Ammonia Measurement
The study 4 evaluates the clinical utility of breath ammonia compared to blood ammonia and finds that breath ammonia may offer clinically important information not provided by blood ammonia. The study 5 suggests that ammonia levels do not guide clinical management of patients with hepatic encephalopathy caused by cirrhosis.
Hyperammonemia
Hyperammonemia can occur in critically ill patients without liver failure, as reported in the study 6. The study finds that these patients have a poor prognosis, although ammonia level per se is not independently associated with mortality.