Thrombosis is a serious condition where a clot forms inside a blood vessel (an artery or vein) in your body or sometimes inside of your heart. This is dangerous because clots that form inside blood vessels can block blood flow. They can also break free and travel elsewhere in your body, and if a clot gets stuck in a critical location like your lungs or brain, that can cause life-threatening emergencies.
Thrombosis can happen to people at any age, but it’s more common as people get older. This condition is also much more likely to happen when you have certain medical conditions. Some of those conditions include:
. Atrial fibrillation.
. Heart disease.
Thrombosis is an extremely common problem and is the underlying cause of 1 in 4 deaths worldwide. That’s because thrombosis creates clots that can lead to extremely dangerous conditions. A few examples of the deadly conditions that happen because of thrombosis include:
. Heart attack.
. Pulmonary embolism (PE).
Thrombosis falls into two categories, depending on the type of blood vessel where it starts.
This is thrombosis that happens in arteries, which are blood vessels that carry blood from your heart to the rest of your body. Arterial thrombosis is the most common cause of heart attacks and strokes.
This is thrombosis that happens in veins, which are blood vessels that carry blood back to your heart from your body. Venous thrombosis is the most common cause of pulmonary embolism (blood clot in your lung).
Thrombosis is dangerous because it creates clots that could block blood flow somewhere in your body. That happens in one of two ways:
. Blockage where the clot forms. A clot that forms because of thrombosis can stay in place and grow until it’s big enough to block blood flow. The severity of that blockage depends on where that clot forms and how big it grows.
. Clots that cause blockages in other places. A major risk with thrombosis is that a clot will break free from where it forms and becomes an embolus (more than one is “emboli”). Once it breaks free, it can travel in your blood and end up in blood vessels that are too small for it to pass, which creates a blockage (known as an embolism). This is usually what causes conditions like stroke and pulmonary embolism (PE).
The symptoms of thrombosis depend strongly on the size of the clot and its location. Arterial and venous clots often form in your legs, but can also form anywhere in your body. However, blockages become much more likely to form in areas with very small blood vessels, especially your brain, lungs and farther down in your arms and legs.
Clots that form blockages outside of your organs typically cause symptoms listed below.
Every cell, tissue and organ in your body depends on a steady supply of blood to survive, and arteries are how they get that supply. A clot that blocks an artery will cause a problem called ischemia (iss-key-me-uh), which is when cells start dying because they aren’t getting the blood flow they need.
Early symptoms of ischemia from a blood clot include:
. Visible color changes on your skin. Areas beyond the blockage (meaning the clot is between that area and your heart) will typically look paler than other areas.
. Temperature change in the affected area. Lack of blood flow will make the affected part of your body feel cooler to the touch than other areas.
. Weakness. This can also involve not being able to move the affected body part.
. Numbness or tingling (pins and needles feeling). This can also sometimes involve pain in the affected area.
The symptoms that follow usually are more severe. They include:
. Blisters, wounds or sores. These can happen when skin wears away or tears open.
. Skin sloughing (pronounced “sluffing”). This is when skin falls away or separates from the tissue underneath.
. Necrosis. This causes skin and tissue to die and turn black. The area of dead or dying tissue will spread gradually outward.
Blockages of veins, which are also very common in your legs, limit how quickly blood can make its way back to your heart. That puts too much pressure on your veins, which causes fluid and blood to leak out of them and into surrounding tissues.
When this happens, symptoms typically include:
. Color changes, especially redness or darkening of the affected area.
. Pain, especially around the affected area.
. Swelling from the fluid buildup.
. Skin that feels noticeably warmer than other areas.
Thrombosis can happen for many reasons, but certain conditions are more likely to cause clots to form. These conditions fall under the following types or categories.
Conditions like atherosclerosis, where arteries stiffen because of a buildup of plaque (a waxy substance related to cholesterol) inside them, often cause clots. This happens when a clot forms over a rupture or break in a section of plaque. This is often what causes heart attacks.
. Heart valve disease. Problems with your heart valves, such as mitral valve stenosis (narrowing), can make clot formation more likely.
. Atrial fibrillation. This is a condition where the upper chambers of your heart beat so fast, they can’t pump blood correctly. Blood that lingers in these chambers can form clots, which can then travel elsewhere in your body. Atrial fibrillation is a common cause of stroke.
. High blood pressure and high cholesterol. Both of these conditions, over time, can damage your heart and blood vessels, limit circulation and make it easier for clots to form.
Several conditions and problems can cause your blood to clot more easily. These conditions can happen for the following reasons:
. Inherited or genetic clotting disorders. Several genetic conditions, which you inherit from your parents, can make your blood clot too easily. These conditions are usually treatable but typically aren’t curable.
. Other medical conditions. Certain types of cancer can make blood clots much more likely. Other conditions like HIV, inflammatory bowel syndrome or immune disorders can also cause clotting problems.
. Medical procedures. Surgeries can cause your body to try to clot in ways that can be harmful. That’s why medical providers often prescribe blood-thinning medications after surgery or other types of procedures.
. Medications. Certain medications can cause your blood to clot more easily. In some cases, that’s on purpose. In others, it can be an unexpected and unintended side effect of or reaction to a medication. Certain types of hormonal treatments, including those used in birth control, can also cause blood clotting issues.
. Lack of activity. Sitting or lying still for long periods can cause your blood to circulate poorly in some parts of your body, especially your legs. That makes it easier for clots to form. This often happens to people on long airplane or car trips, people who have some form of paralysis or who are on bed rest. It can also happen to people who aren’t physically active, especially those who sit for extended periods.
Blood clots that get stuck in certain organs typically cause certain symptoms. The symptoms depend heavily on the affected organ.
A clot that gets stuck in your brain causes a stroke. Blockage of blood flow in your brain causes those areas to stop working. If blood flow isn’t restored quickly, permanent damage to those cells is possible. That’s why a stroke is a medical emergency, and getting immediate medical care is critical.
Symptoms of a stroke include:
. Weakness or trouble controlling muscles on one side of your body.
. Slurred or garbled speech.
. Noticeable droop and lack of muscle control on one side of your face.
. Confusion, agitation or otherwise unusual behavior changes.
Blood clots can easily get stuck in your lungs because the blood vessels inside of them are very small. Clots that get stuck there cause pulmonary embolism, a life-threatening condition that needs immediate medical care.
Symptoms of a pulmonary embolism (PE) include:
. Chest pain. This is usually a sharp pain that may feel like a heart attack, though it happens for a different reason. It can also happen in areas around your chest, such as your jaw, neck, shoulder, back or arm. The pain can feel pleuritic, meaning it’s painful to take a deep breath in.
. Sudden trouble breathing (dyspnea). This can happen while you’re active or when you’re resting.
. Coughing. Mucus that you cough up may, but doesn’t always, have blood in it.
. Fast heartbeat.
. Sweating and skin that’s pale, clammy or that has a blue tinge to it (especially your lips or fingernails).
. Dizziness or passing out.
Pulmonary embolisms are most likely to happen because of deep-vein thrombosis, which is when a blood clot forms in a major artery in your leg.
A heart attack happens when a clot forms or gets stuck in your coronary arteries, which supply your heart muscle with blood. There are many symptoms possible with a heart attack, and a few common ones include:
. Chest pain (angina).
. Trouble breathing (dyspnea).
. Dizziness or passing out.
The mesenteric arteries supply blood to most of your digestive tract, especially your small and large intestine. When there’s a blockage in those arteries, it can interfere with how your digestive system works.
If a clot is the cause of the blockage, the symptoms tend to be sudden and include the following:
. Severe stomach or abdominal pain, especially after eating.
. Nausea and vomiting.
. Diarrhea and blood in the stool.
. Bloating or feeling of pressure in your stomach and gut.
A diagnosis of thrombosis usually happens in a hospital. However, healthcare providers may start suspecting it in a healthcare setting like a doctor’s office or an urgent care-type clinic. If it happens outside a hospital, medical professionals will likely treat your case as a medical emergency because of the risk of heart attack, stroke or pulmonary embolism, all of which are life-threatening.
A healthcare provider diagnoses thrombosis based on a combination of your medical history, questions they ask you, a physical examination, laboratory tests, imaging tests and other diagnostic methods. The tests they use may vary greatly depending on the conditions they suspect or are possible.
The following test types are most likely when a healthcare provider suspects thrombosis:
A physical exam is where a doctor looks at different areas on your body for visible signs of a problem. They’ll also feel areas of concern (for problems like swelling, tissue changes or temperature changes), and listen to your heart, breathing and digestive system.
In cases where they suspect thrombosis in your arms or legs, they might listen to the sound of your pulses in your affected limb. That can help them figure out the approximate location of a clot.
Healthcare providers will use a wide range of imaging tests to let them “see” inside your body, too. These tests help with diagnosing and locating blood clots, as well as guide treatment.
Some of the possible tests include the following methods:
. X-rays. This also includes computed tomography (CT) scans, which use a computer to assemble X-ray images into a 3D picture of the inside of your body. These methods may also involve substances that a healthcare provider injects into your body. These substances are highly visible depending on the imaging method, which can help highlight any areas where blood isn’t circulating.
. Ultrasound. Tests that use this involve ultra-high-frequency sound waves that help generate a picture of the inside of your body. The sound waves bounce off different areas inside of your body, much like how dolphins and bats use sonar to “see” in places where there’s no light.
. Magnetic resonance imaging (MRI). This imaging method uses a very powerful magnet and computer processing to create a high-resolution picture of the inside of your body.
Because clotting is something your blood does naturally, lab tests on your blood can help analyze and determine if your blood clots too easily. These tests can also help discover why your blood is clotting and can help decide on possible treatments.
These tests usually look for the following:
. Blood components. This includes several tests that measure certain types of blood cells like platelets and chemical compounds, especially ones that affect clotting.
. Clot-formation markers. These are chemicals that typically only show up in your blood if you have a clot at the time. They can help healthcare providers confirm or rule out an active clot as the source of a blockage.
. Heart damage markers. An example of this is troponin, a protein found in muscle cells. Your heart muscle cells contain a very specific type of troponin that doesn’t occur elsewhere in your body. Damage to your heart cells, such as from a heart attack, causes troponin to leak out of those cells and into your blood. Tests that detect troponin can help confirm or rule out heart attacks, which often happen because of thrombosis.
The possible complications from thrombosis depend strongly on the location of the clot(s), why they formed and treatments used. Your healthcare provider is the best person to explain the potential complications and side effects, as well as any potential risks.
There are several circumstances or health conditions that can increase your risk for this condition. Managing them can help reduce your chance of developing thrombosis and the dangerous conditions that can follow. The circumstances you can influence include:
. Blood pressure.
. Kidney problems.
. Liver problems.
. Your level of physical activity.
. Smoking (or other forms of tobacco use).
When you know you’re at risk for clots, prevention is much easier. The best way to know about your risk is to get an annual physical (wellness visit or checkup). Many conditions that increase your risk for thrombosis are detectable during a checkup long before clots ever form. If your healthcare provider finds any conditions or concerns that increase your risk, they can guide you on what to do to care for yourself.
Other ways to prevent clots from forming include:
. Move around. Sitting for long periods can greatly increase your risk of thrombosis. If you work in a job where you sit or hold still for long periods, try taking short breaks. Even standing up and stretching for a couple of minutes can help. For those who are unable to stand up or move about because of health conditions or circumstances, your healthcare provider may be able to offer alternative ways for you to keep your blood moving with activity.
. Quit tobacco or don’t start. Smoking and other forms of tobacco use (including vaping and smokeless tobacco products like snuff or chewing tobacco) greatly increase your risk of thrombosis. Quitting tobacco products or not starting them at all can make a big difference when it comes to prevention.
. Manage your weight with diet and exercise. Eating a healthy diet and getting enough exercise (150 minutes of moderate-intensity activity per week) can help you lower your risk of thrombosis.
. Take your medication. If your healthcare provider prescribes medication, be sure to take it as they instruct, or ask them about how you can take it. The risk of dangerous complications increases sharply if you suddenly stop taking many of the medications that prevent thrombosis, especially blood-thinners. It’s also dangerous to take more than the recommended amount, such as after forgetting to take a dose.
Treatment of thrombosis depends strongly on why it’s happening and what parts of your body it affects. In some cases, such as when it’s happening because of a genetic or inherited condition, thrombosis is potentially treatable but not curable.
Treatment of thrombosis can take several different forms. It can involve medication, surgery, minimally invasive catheter procedures and more. In many cases, thrombosis treatment starts with prevention, keeping clots from forming and becoming a danger.
Treatment of thrombosis can involve any — including various combinations — of the following:
Preventive treatments for thrombosis typically involve a few different classes of medications. These usually include one or more of the following:
. Blood-thinners. These medications keep your blood from clotting too easily. There are different types of blood-thinners, including antiplatelet, anticoagulant and fibrinolytic drugs.
. Blood pressure-lowering medications. Over time, high blood pressure puts too much stress and wear on the inside of your blood vessels. This kind of wear and tear can make it easier for blood clots to form and grow on your vessel walls. Blood pressure medications prevent clots by not giving them new places to form.
. Cholesterol-lowering medications. Your cholesterol levels directly influence the buildup of plaque on the inside of your blood vessels. Lowering your cholesterol limits that buildup.
Acute blood clots (meaning they started very recently) are also treatable with medications. These medications usually include the following:
. Blood-thinners (for the same reasons mentioned under “Preventive treatments” above).
. Clot-busting drugs. These drugs break down existing clots, which is especially helpful when a clot is in a critical area. Drugs like this are common in the treatment of heart attack, stroke and other thrombosis-related conditions.
Healthcare providers may also prescribe other medications, such as pain medications or blood pressure medications, which will ease your symptoms and improve blood flow.
Depending on the location and size of the clot, healthcare providers may be able to go in and remove the clot directly. This kind of clot removal, known as thrombectomy, can happen in a few different ways:
. Surgery. One of the most direct ways to remove a clot is for a surgeon to access it directly and remove it. In some cases, they may also use surgery to do a bypass, where the surgeon takes a section of blood vessel from elsewhere in your body and uses it to construct a bypass, or detour, around an area of another blood vessel that’s very narrow. This restores blood flow to the affected parts of your body.
. Catheter procedures. These types of procedures use a long, thin, tube-like device called a catheter. A healthcare provider inserts this device into a major blood vessel somewhere on your body and steers the catheter through your blood vessels to the blocked area. Once there, they can use devices on the tip of the catheter to break apart and suck up the clot fragments (rheolytic thrombectomy), and/or inflate a small balloon on the tip of the catheter to widen narrow sections of a blood vessel. They can also sometimes place a stent, a scaffold-like device, which acts as a support to hold your blood vessel open.
You should only manage a thrombosis according to guidance from your healthcare provider. Thrombosis is a very dangerous condition, and your healthcare provider is the best person to determine how to safely and effectively treat a clot.
Most people who receive treatment for thrombosis feel better as they’re treated, especially with restoration of blood flow to previously blocked areas. That can happen in minutes or hours, depending on the location and size of the clot and the specific treatments.
In cases where you had severe effects from a clot, especially ones that caused a life-threatening event like a heart attack or stroke, it may be a few days before you start feeling better. That’s especially true if you need surgery or more intensive procedures and care.
Your healthcare provider is the person who bests understands your case. They can tell you more about what to expect, especially regarding your specific circumstances, and answer any questions you might have.
If you have thrombosis, it’s important to get immediate medical care, such as in a hospital emergency room. That’s because thrombosis can very easily become one of several extremely dangerous — and deadly — conditions. The longer thrombosis continues, the more likely it is that one of those dangerous conditions will occur.
How long thrombosis lasts depends on the underlying cause, the treatments and how quickly you seek medical attention. In general, the shorter the time you have thrombosis, the better off you are. That’s why getting medical attention quickly is so critical. While thrombosis may be short-lived (ideally), the dangerous conditions that cause it can be chronic or even life-long. Some of them, especially genetic or inherited diseases and conditions, are ones you have when you’re born.
Thrombosis is a serious condition, but usually isn’t dangerous on its own unless it lasts for longer periods. The problem with thrombosis, though, is that it very easily turns into a dangerous, life-threatening emergency. But with immediate medical care, it’s usually possible to avoid serious complications. However, the longer it takes for that care to start, the greater the danger from this condition (or the conditions that happen because of it). The outlook or prognosis with thrombosis also strongly depends on where it happens and whether or not it affects any other part of your body. A clot that stays in place is a problem, but is usually less dangerous than a clot traveling in your bloodstream. The outlook for this condition can become much worse when a free-floating clot carried in your bloodstream ends up in a critical organ like your heart, brain or lungs. If this happens, timing becomes critical, and minutes may end up deciding whether or not you have a good outcome.
Because thrombosis is usually a short-lived condition, it’s not something you’ll likely have to live with for very long. However, many people have conditions or circumstances that put them at risk for developing thrombosis, and some of those conditions are life-long.
The best thing you can do if you’re at risk of developing thrombosis is to prevent it from happening. That means seeing a healthcare provider regularly, taking prescribed medications, taking care of your overall health and watching for symptoms that indicate you have a problem.
You should seek medical attention anytime you have symptoms of thrombosis, especially symptoms that show part of your body isn’t getting enough blood flow.