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Blood Clots: Types, Causes, Symptoms, Treatment, and more

Blood clots are a serious medical issue, and can be life-threatening if left untreated. They are caused by a number of conditions and can affect people of all ages and genders. While not everyone is at risk for blood clots, it is important to be aware of the potential dangers.

What is a blood clot?

A blood clot is a mass of blood that forms within the body. Clots are common and typically don’t cause any problems. However, they can become serious if they break loose from their original site and travel to other parts of your body. This is called an embolism, or when the clot blocks one of your blood vessels.

Blood clots are usually made up of platelets and fibrin. Platelets (1) help stop bleeding by forming a plug at a wound site, while fibrin (2) helps stabilize the clot.


There are two types of clots: thrombosis and embolism.

Deep vein thrombosis (DVT)

DVT is when a blood clot forms in one of your deep veins. These are the larger veins that run through your leg and arm and are responsible for transporting blood back to your heart.

A DVT occurs when something disrupts the natural flow of blood in your body — for example, if a blood clot forms in a vein. It can lead to serious complications such as a pulmonary embolism (PE).


An embolism occurs when part of a deep vein thrombosis breaks off and travels through the bloodstream until it reaches an artery that’s narrow enough to block off completely causing an injury or death in tissues beyond that point (stroke).

In the heart, an embolus can be a clot that travels from another part of the body to block blood flow in an artery of the heart. This causes a heart attack.

In the brain, an embolus is usually a fragment of the plaque that breaks off and travels through the bloodstream until it lodges somewhere in a blood vessel.

An embolism can also occur elsewhere in the body, such as in a vein or artery leading to or from the lungs (pulmonary embolism (3)).

How do blood clots happen?

A blot clot happens when a blood vessel leaks or breaks open, allowing blood to leak into the surrounding tissue. The leaking blood causes swelling, which can damage tissue, such as brain cells or nerves in your eyes. This damage can lead to serious complications, including stroke or blindness.

Bleeding into your body from an artery (a large blood vessel) usually happens only once in a lifetime but may happen more than once for some people with certain medical conditions like high blood pressure, heart disease, and diabetes.


Blood clots can be caused by a variety of factors, including trauma, surgery, or immobility. The risk of developing a blood clot increases with age and certain lifestyle habits. There are 6 main causes of blood clots developing.

1. Age

The main cause of blood clots is age. As you get older, the lining in your veins thins out and becomes more prone to developing clots. Blood thinners help prevent this by making it harder for the clotting process to occur.

People who have had abnormal heart rhythms or chest pain caused by blood clots should talk with their doctor about whether they need medication to prevent further problems. Blood clots can also be caused by certain medical conditions, such as cancer or other types of cancer treatments.

2. Traveling frequently

Traveling frequently is a common cause of blood clots. If you travel frequently, you’re more likely to develop a blood clot than if you rarely travel or never travel at all.

When traveling by plane or train, it’s important to move around as much as possible and avoid sitting still for long periods.

3. A sedentary lifestyle

A sedentary lifestyle is the main cause of blood clots. Clots in your blood can be caused by too much sitting and not enough exercise.

Blood clots are most likely to occur when you are sitting or lying down for long periods. When you sit or lie down for too long, you may notice that your legs feel heavy or swollen. This is a sign that your blood isn’t flowing as it should through your veins and arteries.

Exercise helps move and pump blood through your body so that it can reach all areas like your heart and brain without getting stuck in one place (4). Exercise also increases the amount of oxygen-rich blood flowing through your lungs and into your heart. This helps keep your circulation healthy overall.

4. Obesity

Obesity is the main cause of blood clots. Fat tissue produces more estrogen than other tissues in the body, which can contribute to blood clots.

Fatty tissue may also reduce the ability of small particles in the blood that contribute to clotting to stick together. In addition, fat cells produce hormones that affect how blood clots form and dissolve.

In people who are overweight or obese, blood vessels can become damaged (5) from carrying excess fat around the body. This may make them more likely to develop dangerous blood clots that form in veins in the legs or lungs.

5. Genetics

Genetics is believed to be the main cause of blood clots in many cases. If you have a family member who has had blood clots, it’s important to talk with your doctor about your risk factors and what you can do to prevent them from happening again. 

In some cases, certain genetic mutations may make it more likely for you to develop blood clots. This is called thrombophilia.

6. Smoking

Smoking can increase your risk of getting a blood clot in two ways. It makes your blood thicker by reducing the amount of fibrinogen — a protein that helps your blood to clot — in your body. The nicotine in tobacco also reduces the amount of fibrinogen in your blood.

This means that it takes longer for a clot to form when you’re not smoking, but it also means that when you do get one it’s more likely to be dangerous because it’s harder for your body to break down and stop – even if you have received treatment like heparin or warfarin.

When you smoke, chemicals called nitrosamines go into your lungs and get absorbed into your bloodstream. They cause damage to cells in the walls of your arteries which makes them more likely to become blocked with fatty plaques (atheromas (6)).

These plaques narrow the arteries and make them less flexible so they can’t expand easily when your heart beats fast (or pumps more strongly) during exercise or stress. If an atheroma bursts inside an artery close to where it meets a vein.


Blood clots can occur in almost any area of the body but are most often found in your leg veins or lungs. You can get blood clots without knowing it, and some symptoms may seem unrelated to a blood clot.

Watch for changes in your body, such as tiredness, pain, swelling, or headaches. If you experience any of the following symptoms after a fall, an accident at work, or anytime you suffer from trauma, then it is possible that a blood clot has formed.

1. Swelling and inflammation

Swelling is a common sign of blood clots. This is because blood clots are made up of red blood cells and the plasma protein known as fibrinogen. The red blood cells can’t pass through the walls of the arteries, so they start to accumulate in these small pockets or spaces within the artery wall. This causes the space to fill up with fluid that contains red blood cells, fibrinogen, and other substances that were present in the bloodstream.

If you notice swelling in your limbs, it’s important to see a doctor right away. You should also tell your doctor if you experience swelling in your face or neck, as this can be an indicator of a heart attack or stroke (7).

2. Pain in the limbs

Pain in the limbs is a common symptom of deep vein thrombosis. The pain usually occurs in the calf, thigh, hip, or buttock and may be accompanied by swelling and redness.

The pain occurs because the blood clot blocks the flow of blood through the vein. When this happens, it causes inflammation and swelling of the vein walls. This can also cause pain when you move your leg.

3. Color change in the skin

Although it’s not always possible to see blood clots, they can leave a mark on the skin. The discoloration may be a sign that you have blood clots in your body, according to the Mayo Clinic.

When you have a blood clot in your leg or arm, it generally shows up as bruising and swelling. These bruises can be either black or blue depending on the amount of blood trapped within the clot. In addition to color change, you might also experience pain or tenderness in the area where your blood clot is located.

The first thing people notice about a blood clot is that it’s red or purple. Some other symptoms can help you tell if you have a blood clot. If you notice any of these signs and symptoms, call your doctor right away:

Red or purple patches on the skin. These are called petechiae, and they’re tiny red spots caused by bleeding under your skin. Petechiae can appear anywhere on your body but tend to be most common on your legs, hands, and face.

4. Trouble breathing

Blood clots can cause trouble breathing because they block the flow of oxygen-rich blood to body organs, including your lungs. This causes your heart to work harder to pump blood into your lungs so that it can be oxygenated.

It also means that your heart has less energy available for other functions like pumping blood out of your heart to all parts of the body. Thus, your heart can’t beat as fast or strongly as it should, which leads to low blood pressure and dizziness.

5. Vision issues

It’s not uncommon for people to experience temporary visual symptoms when they are having a blood clot. The most common symptom is blurry vision, but you may also notice that things look different, or that you have halos around lights.

Blood clots in the brain are also the cause of stuttering issues. They can occur during surgery or from injuries that lead to bleeding in the brain. When this happens, it’s important to seek treatment as soon as possible because it can affect your ability to speak clearly and fluently.

6. Feeling nauseous or vomiting

Nausea and vomiting are symptoms of a wide variety of conditions, including viral infections, the flu, food poisoning, appendicitis, ulcers, other stomach disorders, kidney disease, and urinary tract infections.

Blood clots in the veins can cause nausea and vomiting by blocking blood flow through the veins. This can happen if you’re taking birth control pills or hormone replacement therapy.

Blood clots in the veins aren’t usually serious and don’t require treatment unless they become painful or cause swelling or pain in your limbs or abdomen. Vomiting that lasts longer than 24 hours requires medical attention because it can be a sign of something more serious.

7. High blood pressure

High blood pressure is a warning sign for heart attacks and strokes (8). But it can also be a warning sign for other problems, including blood clots in the veins.

High blood pressure can make you feel tired, dizzy, or lightheaded, even when you’re not doing anything active. You might feel this way if you have a headache, aching muscles, or feel nauseous. High blood pressure also puts extra strain on your heart and can damage your arteries over time. This can lead to serious health problems such as heart disease or stroke.

If you have high blood pressure, it means that the force of your heart’s contraction isn’t enough to push the blood out of your heart and through the rest of your body. It’s known as elevated blood pressure because it’s higher than normal.

8. Diarrhea or stomach pain

Diarrhea is a common symptom and one that often goes hand in hand with other symptoms of deep vein thrombosis.

When blood clots form, they can reduce blood flow through the veins they block. This means less oxygen-rich blood reaches organs throughout your body, including your intestines.

The reduced oxygen supply can cause symptoms like abdominal pain, cramping, nausea, vomiting, constipation, or diarrhea. Diarrhea may also occur when bacteria invade damaged tissue after a blood clot has formed.

Symptoms of a blood clot in the heart (heart attack)

Blood clots can be dangerous, but they’re not always easy to detect. When it comes to the heart, symptoms of a blood clot may not be immediately noticeable.

One of the most common places for a blood clot to form is in the heart. This type of clot is called a coronary thrombosis and is sometimes called a “heart attack.” While it’s true that most people who have heart attacks do feel chest pain, some don’t experience any symptoms at all.

The main symptom of a blood clot in the heart is chest pain. This can be mild to severe and can last for a few minutes or several hours.

Other symptoms include:

  • breathlessness
  • a high temperature (fever) of 38C (100.4F) or above
  • a rapid heartbeat (tachycardia (9)) – this may be fast enough to show up on an ECG test
  • shortness of breath, particularly with exercise
  • swelling of one leg – this may be caused by fluid leaking into the tissues due to a leaky heart valve


If you have a blood clot, it’s important to treat it. The main treatments are:

Anticoagulants — These medications help thin the blood and prevent it from clotting too much. Examples include warfarin (Coumadin), dabigatran (Pradaxa), rivaroxaban (Xarelto), and apixaban (Eliquis). Anticoagulants are prescribed for patients who have an increased risk of developing blood clots, such as those who have recently had hip or knee replacement surgery, deep vein thrombosis, or pulmonary embolism.

Injections — Injections of heparin or an alternative medicine called fondaparinux, which is similar to heparin but doesn’t need to be given as often. These medicines keep existing clots from growing larger or new ones from forming. They aren’t as effective as blood thinners and don’t prevent heart attacks or strokes caused by blood clots in the arteries leading to the brain (carotid artery disease).

Antiplatelet therapy — Antiplatelets work by preventing platelets from sticking together to form clots. Examples include aspirin, Plavix, and Pradaxa. Antiplatelet therapy is usually prescribed after you have a heart attack or stroke because these medications reduce your risk of having another event by keeping your blood from clotting too much while it’s trying to heal itself after injury (10).


If you know you’re at high risk for blood clots, your doctor may prescribe a medication to significantly reduce your risk. In addition to the medication, there are things you can do to prevent blood clots from happening in the first place. Do your best to avoid dehydration, always use compression socks, and don’t forget to walk around daily!