Fasting Before Bloodwork Is Outdated for Most Patients
Fasting Before Bloodwork Is Outdated for Most Patients
• Publisher: Medscape
• Date Published: July 17, 2025
1. In the past, patients were routinely asked to fast before doing blood tests, especially in the early morning. This led to long morning lines and inconvenient scheduling.
2. Today, fasting is no longer required for most routine blood tests, such as complete blood count (CBC), electrolytes, and general health screenings.
3. The main reasons fasting was historically required were to evaluate blood sugar (glucose) and cholesterol levels, especially LDL cholesterol.
4. However, diabetes testing has evolved. We now rely mainly on Hemoglobin A1c, which reflects the average blood glucose level over the past 3 months and is not influenced by meals. Therefore, fasting is no longer needed for most diabetes screening.
5. Regarding cholesterol: LDL is usually calculated using total cholesterol, HDL, and triglycerides. Because triglyceride levels can rise slightly after eating, fasting was once required to ensure a consistent and accurate LDL calculation. result.
6. However, research has shown that for most people, eating before a blood test causes only a small change in triglyceride levels, and this does not significantly affect LDL calculations. As a result, non-fasting cholesterol tests are accurate and acceptable for most patients.
7. There are exceptions: if someone has very high triglyceride levels — particularly above 400 or 500 mg/dL — fasting is still recommended. In such cases, not fasting could distort the LDL result or lead to missed risks such as pancreatitis.
8. Newer lipid markers such as ApoB and Lp(a) are not affected by fasting and can provide more accurate assessments of cardiovascular risk.
9. Overall, allowing patients to do their lab tests without fasting is more convenient, just as accurate in most cases, and makes it easier for people to access routine care.
Conclusion:
Most people no longer need to fast before having blood tests. Fasting is still useful for those with very high triglycerides, but for the majority, non-fasting bloodwork is accurate and preferred.
Source: http://www.medscape.com/
