Factor VII Activity (1:40)

The Factor VII activity test checks how well factor VII, a clotting protein made in the liver and dependent on vitamin K, is working in your blood. It is a functional assay that measures the ability of this factor to help start the clotting process in a controlled laboratory reaction.

Your plasma is combined with specific reagents to trigger clotting, and the laboratory calculates the activity of factor VII from the response. The term 1:40 refers to a dilution used during the procedure; it is part of the method and does not reflect your personal result.

This test helps find the cause of unusual bruising or bleeding, especially when your prothrombin time (PT) is prolonged. It can identify inherited factor VII deficiency, reveal vitamin K deficiency, show effects of certain medicines, and provide clues about liver function. It is also used to plan safely for surgery or dental work and to monitor treatment if you receive factor replacement.

Results are interpreted with other coagulation tests, such as PT/INR and panels of clotting factors, to give a clearer picture of your clotting system. Knowing your factor VII activity can guide decisions about treatment, timing of procedures, and whether additional testing is needed.

A lower-than-expected factor VII activity can be due to an inherited deficiency, vitamin K deficiency, liver problems, or the intended effect of vitamin K–blocking medicines. Some antibiotics, poor nutrition, or gut absorption issues can also reduce vitamin K and lower activity. Higher-than-expected activity is less common but can occur with inflammation, estrogen-containing therapies, or during pregnancy.

Your care team will look at your symptoms, medication list, diet, and other lab results to interpret what the number means for you. If findings are unexpected, follow-up may include repeating the test with careful sample handling, checking PT/INR, measuring other factors, or performing a mixing study to tell a true deficiency from an inhibitor. In select cases, genetic testing or evaluation of liver and vitamin K status may be considered.