VWD can be difficult to diagnose and frequently goes undetected until a person has an episode of heavy bleeding. The diagnosis is suggested by:

  • Bleeding symptoms (refer to Symptoms)
  • A personal history of excessive bleeding
  • A family history of bleeding symptoms and/or a bleeding disorder (because VWD is a genetic disease)
  • Evidence of unusual bruising or other signs of recent bleeding on physical examination

When VWD is suspected, an individual usually undergoes a series of blood tests that includes1,2:

Complete blood count (CBC)
Measures the number of red blood cells, white blood cells, and platelets. It is useful for determining the presence and severity of anemia and thrombocytopenia

Activated partial thromboplastin time (aPTT)
Measures clotting time and assesses the intrinsic and common coagulation pathways

Prothrombin time (PT)
Another test that measures clotting time and assesses the intrinsic and common coagulation pathways

von Willebrand ristocetin cofactor activity (VWF:RCo)
Measures the ability of a person's VWF to interact with normal platelets. This test may also be called VWF activity or RCo test

VWF antigen (VWF:Ag)
Measures the amount of VWF in a person's blood

FVIII assay
Indirectly assesses the severity of VWD and the likelihood of bleeding by measuring the level of FVIII. Since VWF transports FVIII, very low levels of FVIII could mean that VWF levels are also very low. This assay also helps determine what treatment is necessary

VWF multimer test
Evaluates abnormal results from the tests described above. This test shows the structure of the VWF protein, helping to identify type of VWD

Occasionally, laboratory tests may have to be repeated because various conditions or situations can affect VWF and FVIII levels. These include:

  • Stress, exercise, smoking, or alcohol use
  • Hormonal fluctuations associated with pregnancy or the menstrual cycle
    • The best time to test is during the first 3 days of the menstrual cycle, when hormone levels are the lowest
  • Oral contraceptives and hormone replacement therapy



  1. NHLBI. National Heart, Lung, and Blood Institute. The diagnosis, evaluation, and management of von Willebrand disease. Available at: http://www.nhlbi.nih.gov/guidelines/vwd/vwd.pdf. Accessed August 5, 2013.
  2. James AH. 100 Questions & Answers about von Willebrand Disease. Sudbury, MA: Jones and Bartlett Publishers; 2009.


Sponsored by Grifols and Wisconsin Bleeding Disorders Network