Fibrinogen is an essential clotting factor that helps your body heal from injuries. Low levels can cause excessive bleeding. Keep reading to understand what can cause fibrinogen levels to drop too low and what you can do to increase them.
Causes of Low Fibrinogen Levels
According to the World Federation of Hemophilia, low fibrinogen blood levels account for about 7% of bleeding disorders worldwide, which are more common in women than men .
Causes listed below are commonly associated with low fibrinogen. Work with your doctor or another health care professional to get an accurate diagnosis.
1) Excessive Blood Loss
Low fibrinogen (acquired hypofibrinogenemia) is most often caused by excessive blood loss. This is because most of the body’s fibrinogen has been used up to stop the bleeding .
Medication used to break down blood clots, such as streptokinase, urokinase, and tissue plasminogen activators decrease fibrinogen in cell and human studies [3, 4, 5].
Urokinase is a thrombolytic (“clot-busting”) drug that decreased blood fibrinogen levels by an average of 35% after 24h in a study of 204 patients with stroke .
Other drugs that can decrease fibrinogen include:
- Anti-seizure (epileptic) drugs valproic acid and phenobarbital [6, 7]
- Chemotherapy drugs, likely by inhibiting liver protein production [8, 9, 10]
- Anabolic steroids 
- Muscle pain reliever pentoxifylline, likely by inhibiting fibrinogen production [12, 13]
People with low fibrinogen are recommended to avoid aspirin or other blood thinners that will further decrease their ability to form blood clots unless prescribed by a doctor .
On the other hand, doctors often recommend anticoagulant drugs (such as heparin or aspirin) as an add-on to fibrinogen replacement therapy to help reduce the likelihood of an internal blood clot .
Liver disease can cause low fibrinogen levels by either impairing the body’s ability to produce fibrinogen or over-stimulating the breakdown of clots and consumption of fibrinogen [16, 17, 18].
Leukemia may reduce fibrinogen levels by promoting clot formation and fibrinogen degradation (surveys of 1,304 patients, 17 patients, and 379 patients) [19, 20, 21].
4) Genetic Disease
Congenital hypofibrinogenemia is characterized by low blood levels of fibrinogen (between 0.5 and 1.5 g/L) with prolonged clotting times .
Caused by either a dominant or recessive mutation, this condition is estimated to affect as many as one in 100 people. Many of these people present no symptoms, maintaining enough fibrinogen to clot minor injuries (survey of 100 patients; genomic database analysis including approximately 140,000 people) [23, 24, 25, 26].
Congenital afibrinogenemia is characterized by extremely low blood levels of fibrinogen, (less than 0.1 g/L). Clotting time is unable to be determined because the blood never clots .
It is a recessive disease, meaning that both parents must have the genetic mutation for their child to acquire the disorder, which affects approximately 10 people per million in the general population. Afflicted individuals are typically diagnosed as infants (survey of 155 participants; genomic database analysis including approximately 140,000 people) [22, 28, 24].
Congenital hypodysfibrinogenemia includes low levels of fibrinogen as well as structural abnormalities in the molecule that do not allow it to properly create clots [22, 29].
It is autosomally dominant, and likely more common than afibrinogenemia (extremely low blood fibrinogen) and hypofibrinogenemia (low blood fibrinogen) in the general population .
This disorder sometimes coexists with plaque build-up in the kidneys that eventually leads to kidney failure .
Fibrinogen Storage Disease
Fibrinogen storage disease is a genetic disorder characterized by low blood levels of fibrinogen as well as a liver disease [31, 32, 33].
The liver disease is caused by excessive storage of fibrinogen in liver cells and is exclusively associated with dominant mutations in the FGG gene [33, 34, 31].
The disease typically manifests in childhood and is estimated to affect up to one person per 100 (single case study; genomic database analysis including approximately 140,000 people) [31, 24].
Health Risks of Low Fibrinogen
1) Excessive Bleeding and Slow Healing
The most common symptoms of low blood fibrinogen levels are prolonged bleeding and easy bruising, especially after an injury or surgery .
Many people also experience longer healing times, spontaneous bruising in their muscles (hematomas), and occasional intestinal bleeding [35, 23].
People with very low blood levels of fibrinogen are also likely to experience spontaneous bleeding, especially around the gums and joints .
2) Pregnancy Complications
Women with low fibrinogen blood levels are more likely to have abnormally heavy menstruation and pregnancy complications, which can lead to miscarriage [36, 37, 27, 38].
3) Harmful Blood Clots
Paradoxically, people with extremely low fibrinogen levels may actually be more susceptible to free-floating clots that block blood vessels. This may be because fibrin, a breakdown product of fibrinogen is not present to inhibit the formation of these internal clots [39, 40, 41, 42].
How to Increase Fibrinogen
Low fibrinogen is usually caused by an underlying health condition. The most important thing is to work with your doctor to find out what’s causing your low fibrinogen and to treat the underlying condition.
If your medication is affecting your fibrinogen levels discuss alternatives or dosage with your doctor or another healthcare professional.
1) Fibrinogen Replacement Therapy
Depending on your levels and the underlying condition, your doctor may prescribe fibrinogen replacement therapy.
Replacing fibrinogen can help prevent and treat excessive bleeding, especially during pregnancy [43, 44, 45].
Replacement therapy may come in the form of a plasma (blood)-derived fibrinogen concentrate of cryoprecipitate (frozen plasma containing high concentrations of fibrinogen) [46, 43].
Protein, in particular, is necessary for healthy levels of fibrinogen. Protein-deficient animals have low fibrinogen compared to their properly-nourished counterparts .
A study of 16 individuals also found that fibrinogen increased by 20 to 40% directly after the participants drank a protein shake or balanced-meal shake, but not after drinking water .
However, protein deficiency is very rare in humans. In addition, giving your body the building blocks it needs to create fibrinogen may only help if your liver is healthy and if you don’t suffer from a genetic disorder.
When your fibrinogen is low, your body can’t create blood clots and heal injuries. Women with low levels are at risk of pregnancy complications.
Fibrinogen levels drop as a result of traumatic injuries and blood loss, liver disease, leukemia, certain medications, or genetic disorders.
Your doctor will prescribe treatment based on the underlying cause. Some people require fibrinogen replacement therapy.