Do Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT), Blood Urea Nitrogen (BUN), and Blood Urea Acid (BUA) and creatinine tests require fasting?

From the Guidelines

AST, ALT, BUN, BUA (uric acid), and creatinine blood tests generally do not require fasting. These common laboratory tests measure liver function (AST, ALT), kidney function (BUN, creatinine), and uric acid levels (BUA), and can typically be performed at any time of day regardless of food intake 1. The tests are used to assess liver damage, kidney function, and uric acid levels, and are often part of a routine laboratory panel.

Key Points to Consider

• The American College of Radiology recommends that these tests can be performed without fasting 1
• However, for the most accurate results, it's best to maintain your normal diet and avoid excessive alcohol consumption for 24 hours before the test
• Some physicians may still recommend fasting for 8-12 hours before these tests if they're being done as part of a comprehensive metabolic panel that includes other tests like glucose or lipids, which do require fasting
• Food and beverages can temporarily affect certain blood values, so it's essential to follow your healthcare provider's instructions, as they may have specific requirements based on your medical history or the complete set of tests being ordered 1

Important Considerations

• The tests are used to assess liver damage, kidney function, and uric acid levels, and are often part of a routine laboratory panel
• The American College of Radiology provides guidelines for the appropriateness of imaging tests, including those for abnormal liver function tests 1
• It's essential to follow your healthcare provider's instructions, as they may have specific requirements based on your medical history or the complete set of tests being ordered 1

From the Research

Laboratory Tests

• The tests mentioned, such as AST, ALT, BUN, and creatinine, are commonly used to assess liver and kidney function 2, 3, 4, 5, 6.
• These tests can be used to diagnose and monitor various conditions, including liver disease, kidney disease, and heart failure 3, 4, 5.

Fasting Requirements

• There is no explicit mention of fasting requirements for these tests in the provided studies 2, 3, 4, 5, 6.
• However, it is generally recommended that patients fast for a certain period before undergoing blood tests to ensure accurate results, but this may not be necessary for all tests, including AST, ALT, BUN, and creatinine 6.

Test Interpretation

• The results of these tests can be interpreted in various ways, including comparing them to reference intervals or looking for patterns of elevation or decrease 2, 3, 4, 5.
• For example, a high BUN/creatinine ratio can be a prognostic indicator in patients with heart failure, while elevated ALT and AST levels can indicate liver damage or disease 3, 4, 5.

Quality Improvement Initiatives

• Reducing unnecessary laboratory testing, including AST and BUN tests, can lead to significant healthcare cost savings 6.
• Implementing guidelines and education for appropriate testing, as well as removing unnecessary tests from order sets, can help reduce the frequency of unnecessary testing 6.