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10 Hidden Causes of High Fibrinogen + Risks & How to Lower It

Written by Biljana Novkovic, PhD | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:
Stress can lead to high fibrinogen levels

As a clotting factor, fibrinogen is essential for the body’s healing processes. However, high levels can be harmful to your health. Read on to understand the hidden causes and risks of high levels and how to lower fibrinogen.

Hidden Causes of High Fibrinogen Levels

Causes listed below are commonly associated with high fibrinogen. Work with your doctor or another health care professional to get an accurate diagnosis.

1) Infections, Injury, or Inflammation

Fibrinogen is a positive acute phase protein, which means that its production is increased during injury, infection, and inflammation [1, 2, 3, 4].

2) Stress

Multiple studies (158 participants; 636 participants) have found that fibrinogen levels increase immediately after a stressful task [5, 6].

In addition, a study with 302 people determined that people with high cortisol levels also had elevated fibrinogen [7].

This relationship is possibly due to the increased production of the fibrinogen genes (FGA, FGB, and FGG) by IL-6, an inflammation-promoting cytokine [8].

Stress can quickly increase your fibrinogen levels.

3) Pregnancy

Pregnant women experience elevated levels of fibrinogen, probably to prevent excessive bleeding when giving birth [9, 10].

As pregnancy progresses, fibrinogen concentration increases up to three times its normal range and then returns to baseline 4 to 6 weeks after delivery [11, 12].

Fibrinogen levels normally rise throughout pregnancy to prevent excessive bleeding during childbirth.

4) Smoking

Multiple studies (9,127 participants; 200 participants; 11,059 participants) have found that smokers and ex-smokers have significantly higher fibrinogen levels than non-smokers (up to 53% more fibrinogen, and up to 11% more, respectively) [13, 14, 15].

Smoking more seems to further increase fibrinogen, and fibrinogen levels do not return to normal until a person has refrained from smoking for about 15 years (11,059 participants; 118 participants) [15, 16].

Smokers who had diabetes and/or high cholesterol had especially high fibrinogen (200 participants; 118 participants) [14, 16].

Smoking increases fibrinogen levels, which take years to return to normal even after people quit.

5) Birth Control Pills

Studies suggest oral contraceptives can increase fibrinogen levels, especially those with high estrogen concentration (randomized crossover study with 28 participants for 16 weeks; survey of 200 women) [17, 18, 19, 20].

Estrogen may elevate fibrinogen by increasing the expression of the FGG gene and production of the protein, as seen in rats [21].

As shown in a study with 194 participants, this effect was compounded in women who smoked while on birth control [22].

On the other hand, multiple studies (trial of 152 women for 1 year; 29 women for 6 months; surveys of over 5k women) have found that hormone replacement therapy may help reduce fibrinogen levels in postmenopausal women, though the effect appears to be minimal [23, 24, 25, 26].

Birth control pills increase fibrinogen levels, especially in women who smoke.

6) Genetic Mutations

Multiple studies (895 participants; 1,002 participants; 7,329 participants) estimated that genes account for 34 to 46% of the individual variation in fibrinogen levels. A number of mutations associated with high fibrinogen levels are discussed here [27, 28, 29].

The inherited disorder homocystinuria increased blood levels of the amino acid homocysteine (3,216 participants), which lab experiments suggest may inhibit the breakdown of fibrinogen, leading to elevated levels [30, 31, 32].

Genes account for up to 46% of the individual variation in fibrinogen levels; variants that increase homocysteine raise fibrinogen.

7) Age

Multiple studies (9,127 participants; 72 participants; 12 participants; 3,967 participants) have found that older people tend to have higher levels of blood fibrinogen, with concentrations increasing around 0.1 – 0.2 g/L each decade [13, 33, 34].

8) Cold Temperatures

Cold temperatures increase fibrinogen levels, resulting in chronic elevation during the winter months (2-hour study with 12 participants; yearlong study of 1,002 participants; yearlong study of 24 participants) [35, 36, 37, 38].

Old age and cold temperatures can increase fibrinogen.

9) Diet

Elevated fibrinogen of 206 Japanese emigrants in Hawaii was associated with more iron (red meat) and sugar consumption. This could implicate the prevalence of meat and high glycemic foods in the Western diet, which is also associated with heart disease [39].

A survey of 1.8k people found that high fibrinogen was associated with low blood concentrations of minerals and vitamins, such as iron and vitamin B6, as well as high levels of cholesterol and fatty acids. This suggests that lower fruit and vegetable intake and higher amounts of processed foods, seen in Western diets can increase chronic inflammation and fibrinogen levels [40].

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 [41].

Meat-heavy, high-carb diets increase fibrinogen; diets low in iron and vitamin B6 have a similar effect.

10) Obesity

Multiple studies of over 1.5k people revealed that people who are overweight generally have high fibrinogen [42, 14, 43, 39].

Though a causal relationship has not been proved, the ability of exercise to decrease fibrinogen suggests body fat and chronic inflammation partially determine fibrinogen levels (87 participants; 3,967 participants) [42, 34].

Being overweight or having more body fat may increase fibrinogen levels.

Health Risks of Elevated Fibrinogen

1) Increases the Risk of Blood Clots & Heart Disease

Elevated fibrinogen levels increase the risk of blood clots, which can, in turn, contribute to an increased risk of heart disease.

High fibrinogen is associated with higher rates of heart disease, blood vessel dysfunction, and stroke. By some estimates, high fibrinogen predicts these diseases as well as high blood pressure and smoking [44, 45, 46, 47].

In a study of over 1.3k patients, high fibrinogen levels were also associated with a greater risk of developing heart disease over 18 months [48].

Furthermore, a longitudinal study of 158 participants concluded that people with larger fibrinogen spikes due to stress had poor blood vessel health, and therefore a greater risk of heart disease 3 years down the road [5].

Elevated fibrinogen is linked to high cholesterol, particularly the bad (LDL) kind, in people without any history of heart disease [16, 49].

Fibrinogen and its degradation by-products were also found in the plaque and cholesterol that builds up on the walls of blood vessels and can cause blockage [50].

However, lab and animal studies have been unable to confirm whether high fibrinogen causes heart disease [51, 52, 53, 54].

People with high fibrinogen levels are more likely to suffer from blood clots and heart disease

2) May Promote Inflammation

Fibrinogen activates molecules that increase inflammation (IL-8, MCP-1, MMP-9, Mac-1) while inhibiting molecules that would decrease it (PPARα, PPARγ), both in the blood and the brain [55, 56, 57, 58].

Mice with either low fibrinogen levels or mutated fibrinogen that cannot bind to white blood cells have significantly decreased inflammatory responses [59, 60].

Certain types of bacteria (Streptococcus) bind to fibrinogen in order to promote inflammation during infection [61].

High fibrinogen levels may increase inflammation in the whole body.

3) May Harm the Brain

High fibrinogen levels may predict future cognitive decline, as well as the development of Alzheimer’s disease and dementia [62, 63].

Fibrinogen may increase brain deterioration in Alzheimer’s disease. Cell studies and rat experiments found that by binding to the abnormal brain plaque, fibrinogen increased damage to brain cells and blood vessels, while also promoting inflammation [64, 65, 66, 67].

High fibrinogen was also associated with active brain lesions in a case-control study of 58 patients with multiple sclerosis, possibly by disrupting the blood-brain barrier [68].

Fibrinogen also suppressed the brain’s ability to heal itself in lab experiments. It did this by inhibiting the regeneration of brain cells and the protective myelin sheaths that normally cover them [69, 70].

High fibrinogen levels may damage brain cells and disrupt the blood-brain barrier.

4) Associated with High Blood Pressure

People with high blood pressure often also have elevated fibrinogen [13, 71].

A study of 143 people over 3 years found that increased fibrinogen after a stressful task predicted the later development of high blood pressure. People with stable fibrinogen levels did not develop high blood pressure. For unknown reasons, this effect was found exclusively in women [6].

High fibrinogen levels may increase the risk of high blood pressure, but possibly only in women.

5) May Promote Tumor Growth

High fibrinogen has been correlated with increased tumor growth, while also predicting poor outcomes in patients with uterine, gastric, and kidney cancer [72, 73, 74].

Specifically, fibrinogen increased tumor cell adhesion and survival in the lung tumors of mice [75, 76].

It seems that the pro-tumor effect of fibrinogen is related to its inflammatory action, as well as inhibition of natural killer cells that typically stop cancerous growth [77, 78].

High fibrinogen may worsen cancer outcomes by increasing inflammation and promoting tumor growth.


Most of the causal relationships between fibrinogen concentration and associated diseases remain unclear. More research is needed to make concrete conclusions about the effects of and effects on fibrinogen.

It’s likely that most of the above-described links between fibrinogen and health conditions are bidirectional. For example, fibrinogen increases when there is underlying inflammation (as an acute phase protein in inflammatory diseases, heart disease, cancer) and can also further increase inflammation.

How to Lower Fibrinogen Levels

High fibrinogen is often 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.

For example, if your fibrinogen is high due to an infection or an acute inflammatory process, it will return to normal once the underlying condition has resolved.

If you have a chronic condition such as rheumatoid arthritis, there may be little you can do to affect your levels [79, 80]. However, if your doctor tells you that high fibrinogen is increasing your risk of heart disease, you can make changes that will improve your levels of other heart disease risk factors, such as decreasing bad and increasing good cholesterol.

Some drugs that lower cholesterol can improve fibrinogen levels [81, 82, 83].

In some cases, your doctor may prescribe drugs that reduce blood clotting [84, 85, 86].

Discuss the additional lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

1) Healthy Diets

Foods that improve bad (LDL) cholesterol may also decrease fibrinogen levels, such as healthy fats and dietary fiber [87].

In a double-blind cross-over study, 6 grams of olive oil per day reduced blood fibrinogen levels by an average of 18% in 20 healthy volunteers after 6 weeks [88].

In addition, studies show there’s a link between diets high in red meat, sugar, and saturated fats and high fibrinogen levels. Therefore, eating more fruits and vegetables, and avoiding sugary, processed, and fast foods can help lower fibrinogen levels [39, 40].

Diets rich in healthy fats and fiber can help decrease fibrinogen levels. Avoid sugary, processed, and fast foods.

2) Exercise

Multiple studies have found a correlation between regular exercise and lower fibrinogen levels (surveys of 1,284, 2,398, and 3,967 participants, respectively) [89, 90, 34].

It seems that strenuous exercise, in particular, reduces fibrinogen: 2 studies of 156 (ten weeks) and 8 participants (one week) showed that fibrinogen decreased by 10 to 20% after intense workouts [91, 92].

3) Weight Loss

Lose weight if you are overweight, as obesity can increase fibrinogen levels, likely by increasing chronic inflammation in the body [93].

Regular exercise and weight loss can help lower fibrinogen.

4) Moderate Alcohol Consumption

Multiple studies (117 participants for 1 month; 20 participants for 6 weeks; 11 participants for 12 weeks) have shown that daily moderate alcohol consumption (1 glass of wine or beer) reduced blood fibrinogen levels [94, 95, 96].

A glass of red wine a day for 40 days was seen to decrease blood fibrinogen levels by 8 to 15% in a clinical trial of 69 healthy adults [97].

However, alcohol consumption can have negative effects on your health, so be sure to discuss the optimal amount of alcohol for your health with your doctor or another healthcare professional.

Adding more olive oil to your diet or having a glass of wine a day may help lower fibrinogen levels.

5) Supplements

Initial studies suggest that the following supplements may help decrease fibrinogen levels in humans. However, more large-scale research is needed to confirm their effectiveness in the general population.

  • Omega-3. A meta-analysis (3 trials and 159 participants) found that fibrinogen decreased about 10% after supplementing with an average of 2.4 grams per day of omega-3 polyunsaturated fatty acids [98]. In addition, studies in 20 and 25 participants found that fish oil reduced fibrinogen after 4 – 6 weeks [88, 99].
  • Turmeric, a known remedy for inflammation and heart disease, decreased blood fibrinogen levels in a study of 30 subjects. Fibrinogen can also bind to curcumin (the active ingredient in turmeric) so that it does not degrade as quickly in the bloodstream [100, 101].
  • The traditional Chinese medicines Quyu Jiedu, Xuebijing treatment, and XueFu ZhuYu decoction, reduced blood fibrinogen levels in 2 meta-analysis studies (15 RCTs with 1,364 patients; 11 RCTs with 686 patients) evaluating the use of traditional Chinese medicine for high blood pressure and chest pain from heart disease [102, 103].
  • Nattokinase. A study of 12 healthy participants found that a single dose of 2000 nattokinase, an enzyme derived from fermented soybeans, significantly decreased blood fibrinogen levels after only 4 hours [104].
  • B vitamins, especially B6, B9, and B12, enhance the breakdown of fibrinogen by reducing the amino acid homocysteine [30, 32]. A study of 24 adults found that 5 mg/day of folate for 4 weeks reduced blood fibrinogen levels by an average of 9% [105]. A 4-week regime of vitamin B6, B9, and B12 also reduced blood fibrinogen levels in 21 patients with sepsis [106].

Remember, always speak to your doctor before taking any supplements, because they may interfere with your health condition or your treatment/medications!


In addition to conditions such as injury, infections, or inflammation, several lifestyle factors can increase your fibrinogen levels, including smoking, eating a meat-heavy or high-carb diet, and vitamin B6 and iron deficiency. People who are overweight also tend to have higher fibrinogen levels.

Fibrinogen levels normally rise in pregnancy and with aging. Additionally, people with genetic variants that increase homocysteine are more likely to have high fibrinogen levels.

Your body requires some fibrinogen for optimal health, but high levels can be harmful. If your fibrinogen levels rise too much, you will be at an increased risk of blood clots, inflammation, and heart disease.

To lower your levels work with your doctor to address any underlying health conditions. In addition, you can prevent increases in fibrinogen by exercising on a regular basis and eating a healthy diet. Increase your dietary intake of healthy fats (olive oil), omega-3s, and fiber. Some supplements may also help. If your fibrinogen levels are very high, your doctor may also prescribe fibrate or antiplatelet medication.

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About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.


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