High fibrinogen: what it means and what to do

A high fibrinogen means your liver is making more of it. Usually inflammation is behind it, even mild, or smoking, extra weight, diabetes or pregnancy. On its own it is not a disease, but it is a good reason to look at your heart and your lifestyle.

What high fibrinogen means

Fibrinogen is used to build a clot. When there is inflammation in your body, your liver makes more of it: that is why it rises together with CRP.

The reason is often temporary, such as an infection you have just got over. If it stays high, smoking, weight, diabetes or long-lasting inflammation are usually behind it.

The higher it is, the higher the average risk for your heart and arteries. But fibrinogen alone says little: cholesterol, blood pressure, smoking and blood sugar matter more.

What causes high fibrinogen

There is often more than one. The most common come first.

• An infection or inflammation: Even a mild one, or one that has just passed. It raises it for a few weeks.
• Smoking: One of the most common causes of a fibrinogen that stays high.
• Extra weight and diabetes: They bring mild but constant inflammation, which keeps it high.
• Age and menopause: It creeps up over the years, and after menopause.
• Pregnancy: It rises on its own in pregnancy, especially in the last months.
• Inflammatory disease, kidney disease or cancer: These are less common causes. They usually give other signs too.

Symptoms of high fibrinogen

High fibrinogen on its own causes no symptoms. If there are any, they come from the cause. For example:

• Fever, a cough or burning when you pass urine, with an infection
• Painful, swollen joints
• Tiredness that does not go away, or weight loss for no reason

If you have these symptoms, talk to your doctor.

High fibrinogen, your heart and blood clots

In studies, people with higher fibrinogen have, on average, more heart attacks and strokes. But part of that link comes from smoking, weight and inflammation, which raise both fibrinogen and risk.

Adding fibrinogen to the usual checks improves the risk estimate only a little. That is why guidelines do not ask for it in people who feel well.

A high fibrinogen on its own does not mean you will get a clot. But if you have a swollen, painful leg, sudden breathlessness or chest pain, call 112 or go to the emergency department.

Which tests to read alongside it

These tests help show where it comes from, and how much it matters for your heart.

What your result means

The upper end of the scale, in mg/dL.

• 200 to 400: Normal. Your blood has enough fibrinogen to clot well, and there is no sign of significant inflammation. Nothing to do.
• Above 400: High. Often there is inflammation or an infection. Smoking, extra weight, diabetes, age and pregnancy raise it too. Show your report to your doctor. They usually look at CRP too.

How to lower your fibrinogen

It depends on the cause. Where to start:

• If you have just had an infection, repeating it after a few weeks is usually enough.
• If you smoke, stopping helps: smoking is one of the most common causes.
• Moving every day and losing weight, if you need to, help bring it down.
• With your doctor, check cholesterol, blood pressure and blood sugar: they matter more for your heart.

No supplement has been shown to lower it. Do not take aspirin or other medicines on your own: decide with your doctor.

High fibrinogen: when to worry

Talk to your doctor if:

• Your fibrinogen is above 400 mg/dL and stays high on a second check.
• You have fever, pain or weight loss for no reason.
• Heart attacks, strokes or blood clots at a young age run in your family.
• You have a swollen, painful leg, sudden breathlessness or chest pain: call 112 or go to the emergency department.

Frequently asked questions

Is high fibrinogen dangerous? Not on its own. It is often the sign of a passing inflammation. If it stays high, it is worth looking at smoking, weight, blood sugar and cholesterol with your doctor, as they matter more for your heart.

High fibrinogen: what are the causes? The most common are infections and inflammation, smoking, extra weight, diabetes, age and pregnancy. Less often, kidney disease, inflammatory disease or cancer.

High fibrinogen and high CRP: what does it mean? That there is probably active inflammation. Your doctor looks at your symptoms and, if needed, other tests to find where it is.

Does high fibrinogen cause blood clots? It goes with a slightly higher risk, but on its own it does not mean you will get a clot. Other factors matter much more, such as surgery, being immobile, smoking and medicines that contain oestrogen.

What should I eat with high fibrinogen? No single food lowers it. A lifestyle that reduces inflammation helps: no smoking, moving every day, a healthy weight and a diet rich in vegetables, legumes and whole grains.

Sources

• Fibrinogen Studies Collaboration, plasma fibrinogen level and the risk of major cardiovascular diseases and nonvascular mortality: an individual participant meta-analysis. JAMA, 2005. PMID 16219884
• Emerging Risk Factors Collaboration, C-reactive protein, fibrinogen, and cardiovascular disease prediction. New England Journal of Medicine, 2012. PMID 23034020
• Kamath and Lip, fibrinogen: biochemistry, epidemiology and determinants. QJM, 2003. PMID 14500858
• Mackie and colleagues, guidelines on fibrinogen assays. British Journal of Haematology, 2003. PMID 12716361