From the Guidelines
Fasting is required prior to collection of laboratory tests for glucose, lipid profiles, and other metabolic tests.
Relevant Tests
- Glucose tests: Fasting plasma glucose (FPG) requires an overnight fast of at least 8 hours 1
- Lipid profiles: Fasting serum triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol require fasting 1
Key Considerations
- Fasting duration: at least 8 hours for glucose tests 1
- Sample collection: blood should be drawn in the morning after an overnight fast 1
- Sample handling: tubes with glycolytic inhibitors should be used to minimize glycolysis, and samples should be centrifuged within 15-30 minutes 1
Clinical Implications
- Accurate diagnosis and monitoring of diabetes and metabolic disorders require proper fasting and sample handling procedures 1
From the Research
Laboratory Tests Requiring Fasting
- Triglycerides: require fasting prior to collection, with a recommended fasting time of at least 8 hours 2
- Glucose: require fasting prior to collection, as food intake can significantly affect glucose levels 3
- Creatinine: may be affected by food intake, but the extent of this effect is not well established 3
- C-peptide and insulin: require fasting prior to collection, as food intake can significantly affect their levels 3
- Testosterone: may be affected by food intake, but the extent of this effect is not well established 3
Factors Affecting Laboratory Test Results
- Food intake: can significantly affect the results of certain laboratory tests, such as triglycerides and glucose 3, 2
- Time of sampling: can affect the results of certain laboratory tests, such as total bilirubin, BNP, and cortisol 3
- Fasting duration: can affect the results of certain laboratory tests, such as triglycerides 2
Patient Preparation for Laboratory Testing
- Patients are often not well informed about the fasting requirements for laboratory blood testing 4, 5
- Patients may not arrive at the laboratory properly prepared for phlebotomy 4, 5
- Requesting physicians and laboratory staff play a crucial role in informing patients about the proper preparation for laboratory testing 4, 5