Blood clots form in blood vessels in the body and can cause serious damage and even death if they migrate to the lungs, brain, or heart. Clotting is a natural and important process to stop bleeding, but when clots form without an injury or fail to dissolve after an injury, they can do serious damage. Many health conditions can trigger blood clots, but so can medicines.

Certain medications increase the risks that a person will develop a blood clot, especially hormone-based oral contraceptives. Blood thinners, the drugs used to treat and prevent clots can also cause serious problems, including excessive bleeding.

How Blood Clotting Works

Blood clotting is a natural and important process through which the blood clumps together in response to an injury. Also called coagulation, it is this process that protects us from excessive bleeding. A scrape, a cut, or an internal injury triggers blood clotting as an attempt by the body to stop bleeding. Normally, the clots are dissolved and reabsorbed into the blood as the injury heals and the risk of bleeding is gone.

There are three components in blood clotting to stop bleeding. The first is the narrowing of blood vessels that have been cut or ruptured, to stem the flow of blood. The next is the action of platelets, particles in the blood that are necessary for clotting. These gather around the injury site and stick to it. Finally, proteins in the blood, called clotting factors, help the platelets stick together to form the clot.

What Is a Blood Clot?

Sometimes blood may clot inside a vessel without an injury to trigger the process, or in some situations a clot may not dissolve completely. These blood clots are small clumps of blood that can then travel through the body and become lodged in a smaller blood vessel. When this happens the results can be serious internal damage or even death, depending on where the clot ends up. If a clot can be detected, it can be destroyed before it causes damage, and if someone is predisposed to forming blood clots, medications or devices may be used to prevent them or trap them before they cause harm.

Risk Factors and Treatment

A dangerous clot may exist in a blood vessel because it was triggered by an injury, but failed to dissolve. Blood clots may also arise without injury and there are many possible causes and risk factors for this. These include some factors that may be preventable, including smoking, obesity, prolonged bed rest or sitting for long periods of time, surgery, and medications. Genetics and family history can also contribute to blood clots.

There are also health conditions, which are not necessarily preventable, that may contribute to or cause blood clots to form: heart arrhythmias, pregnancy, stroke, atherosclerosis, hiatal hernias, peripheral artery disease, diabetes, high blood pressure, high cholesterol, factor V leiden, polycythemia vera, and antiphospholipid syndrome. Treating these conditions reduces the risk of developing blood clots.

Blood clots can be treated directly if detected. The first strategy is to dissolve the clot, either with a thrombolytic drug or a blood thinner. A catheter, a long, thin tube, may also be inserted and used to deliver medication directly to a clot. If these measures do not work, surgery may be used to actually remove the clot from the body.

Deep Vein Thrombosis

A blood clot can form anywhere in the body, but the most dangerous form in a major vein. Veins are responsible for taking deoxygenated blood back to the heart, so a clot in a major vein can prevent blood from getting to the heart. This is called deep vein thrombosis, or DVT, a dangerous health condition that can be fatal if not detected and treated. DVT most often occurs in a leg, but it may also occur in an arm or the trunk of the body.

The real danger of DVT is that the clot or a part of the clot may break away and travel to the lungs, causing a blockage that can quickly become fatal. This is called a pulmonary embolism. The blockage in the lungs prevents blood from going where it needs to and if treatment is no administered immediately, it can be deadly.

To prevent a pulmonary embolism it is important to prevent deep vein thrombosis or to recognize and treat it early. Signs of a DVT include swelling and pain in one leg, often in the calf. These are typically the only signs, and even these may not occur. Steps to prevent DVT include avoid sitting for long periods of time, avoiding drugs that cause blood clots, or at least taking them as directed and being aware of the risks, quitting smoking, eating well, exercising, and maintaining a healthy weight.

Even with risk factors minimized a DVT may form without symptoms. If it moves into the lungs and causes a pulmonary embolism, it can be deadly. Signs of a pulmonary embolism include chest pain, shortness of breath, and a cough, potentially with blood. If these signs are connected quickly to a pulmonary embolism, it can be treated with a clot dissolver or blood thinner medication.

Heart Attack and Stroke

Blood clots that form in blood vessels may also cause a heart attack or a stroke. When a clot breaks free and travels through blood vessels, the lungs are just one location where it can have deadly results. In the heart a clot may cause a blockage that leads to a heart attack and in the brain a clot can cause a stroke. Ischemic strokes, those caused by blockages as opposed to ruptures, account for about 80 percent of all strokes.

Controlling for blood clots by controlling risk factors is one important way to prevent or reduce the risk for having a heart attack or stroke. It is also important to recognize the symptoms of having a blood clot in the brain or heart. Prompt treatment, as with a pulmonary embolism, can be life-saving and may minimize any lasting damage.

In the heart, a clot may feel like pain or a sensation of heaviness in the chest. It may also cause discomfort in other parts of the upper torso, including shortness of breath. Other symptoms include light-headedness, nausea, and sweating. In the brain a clot can cause dizziness, a sudden severe headache, changes in vision, difficulty speaking, and weakness in the face or limbs, often on just one side of the body.

Medications Cause Blood Clots

There are many causes and risk factors for blood clots, but a very serious one that everyone needs to be aware of is medication. There are many medications that put people at risk for blood clots and even some that have been taken off the market for causing deadly clots. Hormone replacement therapies, oral contraceptives, and even some common painkillers, like ibuprofen and naproxen have been connected to an increased risk of developing blood clots.

Birth Control and Blood Clots

Oral contraceptives, pills that deliver hormones to prevent pregnancy, are associated with an increased risk for blood clots. For most patients the elevated risk is small and not significant. However, for those women who have other risk factors, using these pills adds to the risk. The newest generation of birth control pills contains a synthetic hormone called drospirenone, and this may increase the risk even more.

In recent years, one of these newer birth control pills, called Yaz, has come under fire for blood clots and marketing practices by maker Bayer. After four years on the market, in 2011, the FDA issued a warning that Yaz, because it contains drospirenone, carries a greater risk of blood clot than other contraceptives. In 2012 the FDA required that Yaz carry a warning stating that the risks of blood clots could be increased as much as three times with drospirenone. Bayer has also faced lawsuits over how it marketed Yaz, with plaintiffs contending that it promoted benefits that were unproven while downplaying risks.

Blood Thinners

Medications that are used to treat or prevent blood clots, called blood thinners or anticoagulants, can be life-saving, but also deadly. They are used mostly to prevent clots in people who are at risk for them because of certain health conditions or because of having surgery. The problem with blood thinners is that they inhibit the clotting process. If not balanced correctly against the risk of clots, these medications can cause excessive bleeding that can quickly become deadly.

Older blood thinners like warfarin or heparin are difficult to balance. Patients must be carefully monitored while on these drugs, with doses changed as necessary. These drugs do, however, have antidotes that can reverse bleeding. Newer blood thinners are supposed to be easier to use, with more uniform doses, but these still carry risks. Some, like Eliquis, don’t have antidotes, so the consequences of bleeding can be severe. Many of the manufacturers have been accused and even sued over claims that they overstated the benefits of their drugs compared to warfarin and downplayed the risk of bleeding.

Understanding risk factors for blood clots, including medications, is important for preventing them. Because these small pieces of clotted blood can cause so much damage, including death, it is crucial that people are aware of the risks, take steps to prevent them, and know the signs that a dangerous clot may have formed.