Is Fasting Required for the Von Willebrand's Blood Test?

The most common test for von Willebrand disease, a complex bleeding disorder, is the factor VIII coagulant test. This simple blood test measures levels of a clotting protein carried by the von Willebrand factor. Patients do not need to fast before the test.

Function

The test for von Willebrand disease indirectly determines levels of the von Willebrand factor. Low levels of the factor VIII coagulant indicate that the von Willebrand factor is missing or functioning improperly.

Effects

Practitioners may recommend that patients fast before certain types of blood tests, including blood glucose tests to measure insulin production. Fasting does not significantly affect levels of the factor VIII coagulant and will not appreciably alter test results.

Theories

One small 1976 study conducted by the Medical University of South Carolina found that patients experienced decreased function of the von Willebrand factor after consuming glucose. This may suggest that fasting, which temporarily reduces blood sugar levels, can slightly increase levels of the von Willebrand factor and the factor VIII coagulant. However, this effect is not significant enough to result in an incorrect test result.

Considerations

Since blood glucose and insulin levels impact the function of the von Willebrand factor, health care providers may suggest that a patient with diabetes follow a specialized diet before the von Willebrand test.

Warning

If you have a known medical condition, do not fast without first consulting your health care provider.

References

• Kids Health: Von Willebrand Disease
• Clincial Endocrinology: Effect of Oral Glucose on Von Willebrand Factor Activity