Fibrinogen
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
A fibrinogen test measures the level of fibrinogen in a blood sample, a protein made by the liver that is essential for normal blood clot formation. It is used to help evaluate bleeding or clotting disorders, and to investigate conditions such as disseminated intravascular coagulation (DIC), liver disease, or abnormal clotting activity.
Why get tested?
To determine whether your fibrinogen level is adequate to allow normal blood clotting, to help diagnose disseminated intravascular coagulation (DIC), to help determine whether you have an inherited fibrinogen deficiency or abnormality. Sometimes fibrinogen can be a non-specific marker of inflammation in the blood, and very occasionally it helps evaluate your risk of developing cardiovascular disease. High fibrinogen levels may rarely be related to an increased risk of venous thrombosis (blood clots).
When to get tested?
When you have unexplained or prolonged bleeding, an abnormal Prothrombin Time (PT) or activated Partial Thromboplastin Time (aPTT) test, or have a relative with a hereditary fibrinogen deficiency or abnormality. To evaluate whether certain abnormalities in a Full Blood Count are due to inflammation or are self-generated. When your doctor wants additional information to help evaluate your risk of developing heart disease.
Sample required?
A blood sample taken from a vein in your arm, or sometimes, via a finger prick (mainly performed in children).
Test preparation needed?
None
What is being tested?
Fibrinogen is a coagulation factor, a protein that is essential for blood clot formation. It is produced by the liver and released into the circulation as needed along with over 20 other clotting factors. Normally, when a body tissue or blood vessel wall is injured a process called the coagulation cascade activates these factors. As the cascade nears completion, soluble fibrinogen (fibrinogen dissolved in fluid) is changed into insoluble fibrin threads. These threads cross-link to form a fibrin net and then stabilise at the injury site. The net adheres there, along with aggregated cell fragments called platelets, to form a stable blood clot. This barrier prevents additional blood loss and remains in place until the area has healed.
How is the sample collected for testing?
A blood sample is collected by inserting a needle into a vein in the arm. As an alternative, particularly in paediatric care, the blood sample is collected by quickly pricking the fingertip with a lancet.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Common questions
Fibrinogen is usually requested with other tests. It helps your doctor to evaluate your body’s ability to form and break down blood clots. Fibrinogen may be used as a follow-up to an abnormal Prothrombin Time (PT) or activated Partial Prothrombin Time (aPTT, or PTT) and/or an episode of prolonged or unexplained bleeding. It may be measured, along with tests such as PT, aPTT, platelets, fibrin degradation products (FDP), and D‑dimer to help diagnose disseminated intravascular coagulation (DIC). Occasionally fibrinogen can be used to help monitor the status of a progressive disease (such as liver disease) over time, or rarely, to monitor treatment of an acquired condition (such as DIC).
Sometimes fibrinogen is requested with other cardiac risk markers such as high sensitivity C‑Reactive protein (hsCRP), to help determine a patient’s overall risk of developing cardiovascular disease. However, some doctors feel fibrinogen measurements give them additional information that may lead them to be more aggressive in treating those risk factors that they can influence (such as cholesterol and HDL. There are no direct treatments for elevated fibrinogen levels.
The doctor may request a fibrinogen test when a patient has unexplained or prolonged bleeding and/or an abnormal PT and aPTT test result. The test can also be used when patients have symptoms of Disseminated Intravascular Coagulation (DIC), such as: bleeding gums, nausea, vomiting, severe muscle and abdominal pain, seizures and oliguria (decreased urine output), or when the doctor is monitoring treatment for DIC.
Fibrinogen testing can also be performed with other coagulation factor tests when there is suspicion that the patient may have an inherited factor deficiency or dysfunction, or when the doctor wants to evaluate and monitor over a period of time the clotting ability of a patient with an acquired bleeding disorder, particularly in liver disease.
In some cases, fibrinogen testing is performed with other tests when the doctor wants to evaluate a patient’s risk of developing cardiovascular disease and rarely the patients risk of blood clot.
Fibrinogen levels reflect clotting ability and activity in the body. Reduced concentrations of fibrinogen may impair the body’s ability to form a stable blood clot. Chronically low levels may be related to decreased production due to an inherited condition such as afibrinogenemia (no production), or to an acquired condition such as liver disease or malnutrition that leads to hypofibrinogenemia (low levels). Acutely (that is, abruptly) low levels are often related to consumption of fibrinogen, such as may be seen with disseminated intravascular coagulation (DIC) and some cancers. They use up large amounts of clotting factors, leading first to inappropriate clot formation then – as levels fall – to excessive bleeding. Reduced fibrinogen levels may also be seen, sometimes, following large volume blood transfusions (as stored blood loses fibrinogen). Fibrinolytic proteins that normally dissolve clots, may also reduce fibrinogen levels by attacking fibrinogen and breaking down fibrin at an accelerated rate.
Normal fibrinogen levels usually reflect normal clotting, but may also be seen when a person has a sufficient quantity of fibrinogen, but the fibrinogen is not functioning normally – called Dysfibrinogenaemia. This is usually due to a rare inherited abnormality in the gene that produces fibrinogen, which leads to the production of an abnormal fibrinogen protein, approximately 50% of patients will be asymptomatic, 25% have bleeding tendency and 25% are at increased risk of developing blood clots. . If clinical findings suggest a fibrinogen problem, other specialised tests may be done to evaluate fibrinogen function further.
Fibrinogen is an acute phase reactant, meaning that fibrinogen concentrations may rise sharply in any condition that causes inflammation or tissue damage. Elevated concentrations of fibrinogen are not specific – they do not tell the doctor the cause or location of the disturbance. Doctors often do not check for elevated fibrinogen levels in these situations because they expect them to be there. Usually these elevations are temporary, returning to normal after the underlying condition has been resolved. Elevated levels may be seen with:
Physiological:
- Pregnancy
- Oral contraceptives
- Hormone Replacement Therapy (HRT)
- Oestrogens
Pathological:
- Acute infections
- Cancers and Hodgkin’s lymphoma
- Coronary heart disease and myocardial infarction (heart attack)
- Chronic DIC (fibrinogen may be monitored for this condition)
- Inflammatory disorders (e.g. rheumatoid arthritis, glomerulonephritis)
- Any acute inflammation
- Stroke
- Trauma
While fibrinogen levels are elevated, they may increase a person’s risk of developing a blood clot and over time they could contribute to an increased risk for developing cardiovascular disease. This is why some doctors occasionally request fibrinogen with other cardiac risk markers.
Blood transfusions within the past month may affect fibrinogen test results. Certain drugs may cause decreased levels, including anabolic steroids, androgens, Phenobarbital, Fibrinolytic drugs (streptokinase, urokinase, tPA) and sodium valproate. Moderate elevations in fibrinogen may be seen sometimes with pregnancy, cigarette smoking, and with oral contraceptives, HRT or oestrogen use.
Dysfibrinogenemia, is a rare coagulation disorder caused by a mutation in the gene controlling the production of fibrinogen in the liver. It causes the liver to make an abnormal fibrinogen, one that resists degradation when converted to fibrin. In about a quarter of patients with Dysfibrinogenaemia, patients can be at risk of thrombosis, predominantly venous thrombosis, (inappropriate blood clot formation in the veins). PT, aPTT, and Thrombin Time are used to screen for this condition which is then confirmed with additional specialised blood tests. Patients with fibrinogen deficiency or dysfibrinogenaemia may experience poor wound healing.
If your fibrinogen concentration is elevated due to pregnancy, or to an acute inflammatory process, it will usually return to normal by itself after pregnancy. If it is due to an acquired condition such as rheumatoid arthritis, there may be very little you can do to affect the result, but once the condition has been treated it will return to normal. If your doctor has told you that elevated fibrinogen concentrations are increasing your risk of cardiovascular disease, you can make lifestyle changes that will affect other cardiac risk factors, such as stop smoking, lose weight, increase exercise, reducing your cholesterol and raising your HDL. There is also some evidence that diets rich in omega‑3 and omega‑6 fatty acids (fish oils) may help reduce fibrinogen levels.
Fibrinogen measures the soluble Factor I (dissolved in the blood) before it has been turned into insoluble fibrin and been cross-linked into a fibrin net. D‑dimer and FDP both help evaluate the status of the fibrinolytic system – the body’s ability to break blood clots apart when they are no longer needed so that they can be removed. FDP is a measurement of all of the fragments of fibrinogen or fibrin, while D‑dimer was developed as a more specific measurement of fragments of cross-linked fibrin, i.e., derived from an established clot.