What Are Clotting Factors?

H. Colledge

Clotting factors, or coagulation factors, are a series of proteins present in the blood and which play essential parts in the clotting process. There are 13 in all, and they are traditionally numbered using Roman numerals from I to XIII. When a blood vessel is cut, tiny blood particles called platelets collect at the injury site and chemicals are released which activate the clotting factors. Clotting then takes place in a sequence of complicated chemical reactions which ends with the creation of a protein known as fibrin. Fibrin forms a network of strands which combines with platelets and blood cells to create a clot.

Fibrin combines with platelets and blood cells to create a clot.
Fibrin combines with platelets and blood cells to create a clot.

There are important reasons for clotting, as without it cutting a blood vessel could lead to an individual bleeding to death. It is also vital that clotting does not occur inappropriately, as a clot blocking a healthy blood vessel can lead to a reduced blood supply to body tissue. This could have potentially serious consequences if that tissue is part of an essential organ such as the heart. In the blood, there are chemicals which break down clots, and normally there is an overall tendency toward dissolving clots. When a blood vessel becomes damaged, and blood loss is imminent, the system shifts toward creating clots.

Liver diseases may cause clotting problems.
Liver diseases may cause clotting problems.

A clotting deficiency can give rise to a bleeding disorder, where a cut is followed by an excessive loss of blood or where internal bleeding occurs. Deficiencies may arise when clotting factors are not produced in adequate amounts or when a specific clotting factor is faulty and fails to work. Causes of clotting problems include some liver diseases, as many coagulation factors are made in the liver. Not having enough vitamin K can also reduce coagulation factor levels, as the vitamin is necessary for the creation of some clotting factors.

The presence of certain proteins are necessary for the process of blood clotting.
The presence of certain proteins are necessary for the process of blood clotting.

Genetic disorders exist in which certain clotting factors are not made. Hemophilia A is a condition in which there is a lack of clotting factor VIII, and, in hemophilia B, there is a deficiency of factor IX. Other deficiencies are found much more rarely.

Platelets are vital for the body's ability to stop bleeding by forming clots.
Platelets are vital for the body's ability to stop bleeding by forming clots.

Hemophilias may be treated by giving the missing coagulation factors in the form of an infusion into a vein. In cases where hemophilia is severe, it may be necessary to administer clotting factors regularly, while in milder cases, infusions may only be required if bleeding occurs or in situations where it is anticipated, such as before surgery. With treatment, most individuals with hemophilia can expect a positive outlook.

Individuals with hemophilia are advised against donating blood.
Individuals with hemophilia are advised against donating blood.

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Discussion Comments


@Sierra02 - Lots of women have Factor V Leiden and go on to have healthy pregnancies. I'm one of them with two very healthy children, ages two and five.

I was on blood thinner injections during both of my pregnancies and was closely monitored. I had to undergo more ultrasounds than what are normally performed during a pregnancy, but my doctor was only checking for blood clotting in the placenta.

I only inherited one copy of the gene from my mother so the tendency for clotting was much lower than if I had had two copies of the gene, one from each parent.


@Sierra02 - I should state first that I'm not a doctor but I have studied genetics and Factor V Leiden, as it is called, is not actually a disease but a gene that is passed on from your parents. There usually are no symptoms indicating that you have it unless, or until you've had a blood clot.

Given your families medical history and now two miscarriages, I can understand your physicians concern. If it's determined that you are positive with Factor V Leiden you will more than likely be put on a blood thinner like heparin, which is safe to take during pregnancy.

Unless there's some other reason for the miscarriages, as long as your under the careful supervision of your doctor, I don't see any reason why couldn't have children of your own!


My family has a history of arterial thrombosis, a condition where the flow of blood in the veins leading to the heart is impaired or deoxygenated.

I'm twenty-six years old and have had two miscarriages in the past three years. I've always been aware of my families medical history but I didn't realize that it could affect my pregnancies, after all, I have six healthy nieces and nephews.

My doctor suggested that I may have inherited a blood clotting factor 5 (V) gene and that I should be tested for it soon before I become pregnant again.

No other information was given to me about it, only that we'll discuss it more on my next visit. I've been searching everywhere trying to find more information on factor v and what it has to do with my miscarriages. Can anyone help me?

What is factor v? And will I be able to have children of my own?

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