Can urea powder cause falsely elevated Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) levels?

Urea Powder and Liver Enzyme Elevations

Based on the available evidence, urea powder supplementation does not cause falsely elevated AST or ALT levels. 1

Evidence Assessment

The most recent and highest quality evidence from Praxis Medical Insights (2025) clearly indicates that there is no evidence in the medical literature linking urea supplementation to hepatotoxicity or liver enzyme elevations 1. This is particularly significant as:

• Urea is naturally produced in the body as part of the urea cycle in the liver
• The American Liver Foundation and National Institute of Diabetes and Digestive and Kidney Diseases have not identified urea powder as a cause of liver enzyme elevations

Common Causes of Elevated Liver Enzymes

When investigating elevated AST and ALT, consider these more likely causes:

• Non-alcoholic fatty liver disease (NAFLD)/NASH: Most common cause in patients with metabolic syndrome or diabetes 1
• Drug-induced liver injury: Various medications can cause significant elevations 1
• Viral hepatitis: Chronic hepatitis B and C can cause enzyme elevation 1
• Alcoholic liver disease: Typically presents with AST:ALT ratio ≥2 1
• Inflammatory conditions: Including autoimmune hepatitis

Factors That Can Affect Liver Enzyme Measurements

Several factors can cause falsely elevated liver enzymes:

• Alcohol consumption: Active drinking with AST >2× ULN should raise caution for false positive liver stiffness measurements 2
• Hemolysis: Can give positive interference on various laboratory tests 3
• Turbidity: Can cause positive interference on several laboratory parameters 3
• Medications: Many drugs can cause true elevations in liver enzymes

Clinical Approach to Elevated Liver Enzymes

When encountering elevated AST/ALT:

1. Classify the elevation:

   • Mild: <5× ULN
   • Moderate: 5-10× ULN
   • Severe: >10× ULN 1

2. Determine the pattern:

   • Hepatocellular pattern (R ≥5)
   • Cholestatic pattern (R ≤2)
   • Mixed pattern (R between 2 and 5) 1

3. Follow-up testing:

   • Mild elevations: Repeat within 1-2 weeks
   • Moderate to severe elevations: Repeat within 2-5 days 1

When to Refer to Hepatology

Consider hepatology referral if:

• Liver enzyme elevations persist >6 months despite interventions
• ALT elevation >5× ULN
• Development of jaundice or signs of hepatic decompensation 1

Key Takeaway

While investigating elevated AST/ALT, urea powder supplementation can be confidently ruled out as a cause of falsely elevated liver enzymes. Focus instead on more common causes such as NAFLD, medications, alcohol consumption, and viral hepatitis when evaluating patients with abnormal liver function tests.