Von Willebrand factor antigen

Clotting · also printed as vWF antigen, VWF:Ag, Von Willebrand antigen, vWF Ag, VWF antigen

Typical UK adult range50 to 200 IU/dL

Blood group O runs lower; the lab may print group-specific ranges.

What this test measures

Von Willebrand factor is a protein that helps platelets stick to damaged blood vessels and carries factor VIII. A low level is the commonest inherited bleeding tendency.

Why doctors request it

Requested for easy bruising, heavy periods or prolonged bleeding after procedures.

What commonly pushes it up

Stress, exercise, pregnancy and oestrogen, which can mask a low value
Inflammation and infection
Increasing age

What commonly pushes it down

Von Willebrand disease, inherited
Blood group O, where typical values run lower
An under-active thyroid

Everyday reasons for a value outside the range

Blood group O lowers it in the general population
Stress at the time of the sample raises it, so repeats are common

About the sample

Best taken when well and not stressed; usually with the activity test and factor VIII.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

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This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.