Fibrinogen Test


What is a fibrinogen test?

A fibrinogen test measures your levels of a blood protein called fibrinogen. Fibrinogen is made in your liver and helps your blood clot.

Low fibrinogen may make it difficult for your blood to clot. If you have symptoms of excessive bleeding, your healthcare provider may order this test to check your fibrinogen levels. Another name for a fibrinogen test is a factor I activity test.

When is a fibrinogen test performed?

Your healthcare provider may perform a fibrinogen test if you have symptoms that could point to low fibrinogen, such as:

You may also have a fibrinogen test if you have:

What are the types of fibrinogen deficiency?

Fibrinogen tests may detect a fibrinogen deficiency. Fibrinogen deficiencies may be genetic, meaning they occur because of a gene change (mutation). They may also be hereditary, meaning your parents pass down the gene mutation to you.

There are a few types of fibrinogen deficiencies:

  • Afibrinogenemia, when you have no fibrinogen in your blood. This disorder is extremely rare, affecting only 1 out of every 1 million people.
  • Hypofibrinogenemia, when you have low fibrinogen levels. Experts don’t know exactly how many people have hypofibrinogenemia, but it’s more common than afibrinogenemia.
  • Dysfibrinogenemia, when you have typical fibrinogen levels, but fibrinogen doesn’t function properly. Similar to hypofibrinogenemia, it’s difficult to estimate the number of people with dysfibrinogenemia because there are a large number of people without symptoms. But it’s more common than afibrinogenemia.

Test Details

How do I prepare for a fibrinogen test?

Your health care provider will give you specific instructions to prepare for a fibrinogen test. Most people don’t need to do anything different than usual. If you take blood thinners, your provider may instruct you to stop them for a brief period before the test.

Drinking plenty of water can make the test go more smoothly. Staying hydrated keeps more fluid in your veins, making it easier to get a blood sample.

What can I expect during a fibrinogen test?

During a fibrinogen test, your health care provider:

  1. Cleans a small area of your arm with rubbing alcohol.
  2. Inserts a needle into your arm vein.
  3. Attaches the needle to a small tube to collect a blood sample.
  4. Removes the needle and covers the area with a gauze pad.

What can I expect after a fibrinogen test?

You can return home and resume your usual activities immediately after the test.

What are the risks of a fibrinogen test?

There are few risks associated with fibrinogen tests. You may have mild bruising or discomfort where the needle was inserted into your arm. These symptoms usually go away within a day or two.

Results and Follow-Up

What do the results of a fibrinogen test mean?

The test measures fibrinogen levels as grams per liter. A typical fibrinogen level is between 2 and 4 grams per liter or 200 to 400 milligrams per deciliter.

If your fibrinogen levels are higher or lower than typical, it could point to:

  • Blood clotting disorders.
  • Fibrinogen deficiency.
  • Irregular fibrinolysis, which is your body’s process of breaking down blood clots that shouldn’t form.

What happens if I have a fibrinogen deficiency?

Your healthcare provider may prescribe treatments to increase your fibrinogen levels if test results show that you have a fibrinogen deficiency.

You may receive a fibrinogen blood product through an intravenous (IV) line. Often, you receive fibrinogen every other day until your fibrinogen levels are in a typical range.

Your health care provider may also give you an IV with fibrinogen at specific times when you have a higher risk of excessive bleeding, such as:

  • After a traumatic injury.
  • Before surgery.
  • During or after childbirth.

A note from Cleveland Clinic

A fibrinogen test measures your levels of a blood protein called fibrinogen. Fibrinogen is produced in your liver and helps with blood clotting. Your health care provider may order a fibrinogen test if you have symptoms of a bleeding disorder or experience excessive bleeding. A fibrinogen test is a blood test, and you typically don’t need to follow special instructions to prepare. If you have low fibrinogen, your provider may prescribe treatment to increase levels.

Last reviewed by a Cleveland Clinic medical professional on 04/13/2022.


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  • de Moerloose P, Casini A, Neerman-Arbez M. Congenital fibrinogen disorders: an update. ( Semin Thromb Hemost. 2013;39(6) 585-95. Accessed 4/13/2022.
  • Genetic and Rare Diseases Information Center. Hypofibrinogenemia, familial. ( Accessed 4/13/2022.
  • Tziomalos K, Vakalopoulou S, Perifanis V, Garipidou V. Treatment of congenital fibrinogen deficiency: overview and recent findings. ( _Vasc Health Risk Manag. _2009; 5:843-848. Accessed 4/13/2022.

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