Protein C helps regulate blood clots and is vital to the process of wound healing. A shortage of protein C can lead to abnormal blood clots and other, serious conditions.

Blood clots can occur both inside and outside the body. They usually form after damage to veins or arteries and often resolve without treatment after the wound has healed.

The formation of a blood clot is called coagulation. Healthy coagulation requires a precise amount of proteins, as well as blood cells called platelets, for effective function.

However, some clots develop without injury and require treatment. The health consequences of these clots can be extremely severe and sometimes fatal.

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Blood clots outside the body are understood from a young age.

The liver makes protein C and releases it into the bloodstream.

This regulates blood clotting by blocking other proteins that promote coagulation.

Protein C deficiency occurs when a person is unable to produce strong enough protein C or do not have enough of the protein in their body.

This deficiency upsets the balance in the bloodstream. Since protein C blocks clotting proteins, the less protein C the body makes, the greater the risk that blood clots might form.

Protein C deficiency can range from mild to severe. Many people with mild protein C deficiency do not develop problematic blood clots.

According to Clot Connect, an information and outreach project of the University of North Carolina, roughly 1 in 500 people may have the inherited form of protein C deficiency. Severe cases of protein C deficiency are less common, affecting only 1 in 4 million newborn infants.

People can inherit or acquire protein C deficiency.

People inherit protein C deficiency due to mutations in one particular gene called the PROC gene. Researchers have identified 270 different mutations that can either reduce production or prevent the full function of protein C.

The risk of a more serious condition increases with the amount of mutations on the PROC gene.

People also acquire the condition through non-genetic means, including:

  • taking blood thinners, such as warfarin
  • liver failure
  • low intake of vitamin K
  • surgical removal of the small intestine
  • a course of antibiotics without adequate nutrition
  • tumors throughout the body
  • clotting disorders due to blood infections
  • bacterial infections in young people

Risk factors

The greatest risk factors for the condition are having a parent with the condition or a family history of abnormal blood clots.

Parents pass the mutation that causes protein C deficiency to their offspring. There is a 50 percent chance of inheriting the condition when one parent has it. More severe cases can occur when individuals inherit mutated PROC genes from both parents.

The following factors increase the risk of blood clots:

  • age
  • surgery
  • a lack of exercise
  • pregnancy
  • an accompanying blood-clotting disorder

The most severe cases of protein C deficiency occur shortly after birth. This is usually the result of a blood-clotting condition called purpura fulminans.

Some people with very low levels of protein C might show no symptoms until puberty. However, they are just as likely to have blood clots and blockages as a person who showed symptoms earlier on.


Individuals may only discover they have protein C deficiency after blood clots and other associated complications occur.

The complications of protein C deficiency can be severe and may lead to emergency treatment. These include:

Deep vein thrombosis

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Longer journeys without movement may slightly increase the risk of DVT.

Deep vein thrombosis (DVT) is a serious condition that can develop among people with even mild protein C deficiency.

DVTs are blood clots that form below the surface of the skin, usually in the arms and legs but also around the brain.

DVTs can become life-threatening when they move through the body and cause blockages in the lungs.

If people with protein C deficiency have several episodes of DVT, a condition called chronic deep vein insufficiency can develop.

This means that the skin in the area becomes discolored, and the swelling grows more serious.

Pulmonary embolism

This dangerous condition may develop after DVT. A pulmonary embolism blocks blood flow to the lungs.

Problems during pregnancy

Protein C deficiency raises the risk of clots for women during pregnancy and after labor. The risk is higher after birth.

Statistics suggest that 1 out of 100 pregnant women with inherited protein C deficiency will develop a clot unless they take blood-thinning medication. Women who are pregnant should discuss preventive options with their doctors.

Purpura fulminans

This is a life threatening condition occurring in infants with severe protein C deficiency.

Purpura fulminans develops soon after birth. Blood clots form in small blood vessels all over the body.

Blood flow stops around these clots, causing cell death. The body uses up blood-clotting proteins quickly, resulting in abnormal bleeding and discolored skin.

Many newborn infants do not survive this condition. However, those who survive remain at high risk for clots and blockages.

Warfarin-induced necrosis

This is a rare and painful condition found in approximately 1 out of 10,000 people who start treatment with warfarin.

Blood clots cause cell death in the breasts, buttocks, thighs, or torso. Bleeding in these areas turns them purple and blue and causes swelling, severe pain, and gangrene.

Treatment will involve immediately switching warfarin to a course of heparin, vitamin K, and protein C concentrate.

The condition frequently requires surgery.

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Staying active may help to prevent blood clots.

Every blood clot is a potential medical emergency.

People should seek medical help immediately if any of the following symptoms appear:

  • cramps, pain, or tenderness in the arms or legs
  • a red or purple color on the skin
  • swelling
  • warmth in the painful area

Blood clots occur in 900,000 people in the United States each year, and 100,000 of these cases will be fatal.

Statistics from the International Society on Thrombosis and Haemostasis show that 1 out of every 4 pulmonary embolisms is fatal.

Seek emergency medical assistance if any of these symptoms develop:

  • shortness of breath
  • chest pain
  • a rapid heartbeat
  • fainting
  • coughing up blood


A blood test is the only way to identify protein C deficiency. Some factors, such as warfarin treatment, can also cause a temporary drop in protein C, so repeat testing may be necessary.

For the most accurate results, wait for at least 14 days after using warfarin to receive testing. Testing family members can help confirm whether the condition is hereditary.

Doctors might also misdiagnose clots and may call for re-testing.

Even people without protein C deficiency should take action to prevent clots. Simple steps include losing weight, quitting smoking, and staying active.

People with protein C deficiency may want to take further steps. This may involve switching medications, such as stopping estrogen therapy and avoiding contraceptives that contain estrogen and progestin.

Individuals who have family members with protein C deficiency should consider receiving testing, even if they have no symptoms.

People should inform staff about protein C deficiency before surgery, pregnancy treatment, long flights, and other situations that involved restricted movement.

Doctors might suggest long-term treatment with blood-thinning medication for people who have had blood clots as a result of genetic protein C deficiency. If clots are not yet a problem, doctors usually recommend blood thinners only when a person faces an increased risk of blood clots, including:

  • after surgery
  • when using a catheter
  • during long periods without movement

People can supplement low protein C levels with a synthetic concentrate at these times. This can also reduce the dosage of blood thinners prescribed for long-term users.

Protein C deficiency is a shortage of one particular protein that is vital to regulating blood clots throughout the body.

If there is not enough protein C in the body, a person runs the risk of a potentially fatal blood clot, including DVT and pulmonary embolism. An individual will often inherit the condition from one or both parents and blood-clotting medications, such as warfarin.

Treatment includes changing medication and supplementing protein C with a synthetic concentrate.


Is there any way to supplement protein C from the diet?


No, there is no way to supplement protein C from your diet. With protein C deficiency, you are unable to make the enzyme protein C.

There is no dietary supplement for protein C. If you are in a medical situation where you need protein C, doctors will have to give you protein C concentrate.

Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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