Know the Risk Factors for Deep Vein Thrombosis and Other Serious Blood Clots.

Know the Risk Factors for Deep Vein Thrombosis and Other Serious Blood Clots.

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Each year, about 900,000 people in the U.S. develop a venous thromboembolism—a serious blood clot that can form in any blood vessel of your body. When a clot develops in a blood vessel in the lungs, it is called a pulmonary embolism (PE). In the arms, legs, pelvis, or abdomen, it is called a deep vein thrombosis (DVT)

Blood clots can lodge in the blood vessels or travel to other areas of the body, such as the heart, lungs, or brain. These obstructions can cut off blood supply to the brain, causing a stroke.

DVTs and PEs are not just “older people’s” diseases, and the risk factors for blood clots are more common than many people realize. The Centers for Disease Control and Prevention (CDC) estimates that 5-8% of people in the U.S. have at least one genetic risk factor that makes them more susceptible to clots.

What’s more, certain health choices and lifestyle behaviors, such as having a baby or not getting enough regular exercise, also increase the risk. 

Blood clots are medical emergencies—25% of patients with a PE die suddenly, and approximately 10-30% of people with a DVT die within a month of developing one. And blood clots can come back. Approximately one-third of patients who have a clot develop another within 10 years.

However, with fast diagnosis—and specialized care—DVTs and PEs can be treated. MedStar Health is a quaternary health care facility and Level 1 trauma center, which means we provide highly specialized and advanced care for emergencies such as DVTs and PEs. The medical and surgical interventions we offer are not widely available at community hospitals.

It’s important to understand the signs and symptoms of DVTs and PEs, as well as your personal risk factors. With proper planning, many blood clots can be avoided.

Symptoms and signs.

Not all blood clots are dangerous. In fact, clotting is a normal response to an injured blood vessel. Blood clots are made of platelets and a stringy substance called fibrin. When combined, these substances stop up an injury or wound, allowing it to heal.

A venous thrombus is a clot that develops in a vein where it doesn’t belong. Signs of a thrombus can include:

  • Redness
  • Swelling
  • Pain

If the clot moves through the body, such as to the lungs or brain, it is called an embolism. Signs of an embolism mimic those of a thrombus and also can cause:

  • Coughing up blood 
  • Difficulty breathing 
  • Heart palpitations
  • Dizziness
  • Low blood pressure

While everyone should know these symptoms, some people are at increased risk.

Did you know? Symptoms of a dangerous #BloodClot include redness, swelling, dizziness, and fatigue. Find out what to look for and what to do if you spot a clot. #DVTAwareness #BloodClotAwarenessMonth:
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7 factors that increase the risk of DVT or PE.


1. Pregnancy and the postpartum period.

During pregnancy and the three months after giving birth, the body goes through physical and hormonal changes that increase the risk of developing clots. Blood clots form more easily during pregnancy. 

Also, as the fetus grows, it presses against the blood vessels in and around the pelvis. This pressure can narrow or damage these vessels. Limited activity or immobility, such as during bed rest, also increases the risk by reducing circulation in the arms and legs.

Even very fit and healthy patients can develop pregnancy-related blood clots. Tennis star Serena Williams experienced blood clots in the past and had another after giving birth to her daughter. Though she recognized her symptoms right away, Williams had to fight to make her care team understand that she needed help.

Our MedStar Health Labor & Delivery team is specially trained to diagnose and secure treatment for clots. Tell us if you have a history of blood clots, if you have other risk factors, or if you feel like something isn’t right. 

2. Birth control pills or hormone replacement therapies.

Hormonal birth control pills generally use a combination of estrogen and progestin to inhibit ovulation and prevent pregnancy. But estrogen also helps drive clot formation, and increased estrogen levels can heighten the risk of DVT or PE.


Generally, young and healthy people develop fewer hormone-related clots than older patients or those with underlying health problems. However, smoking and other factors increase the likelihood of developing a clot while taking birth control pills.  For most young and healthy patients considering birth control, the risk of health complications from pregnancy and giving birth are greater than the risk of developing blood clots while on these medications.

Research suggests that postmenopausal
hormone estrogen replacement therapy also can increase the risk of DVT and PE. This risk is higher in patients who have other contributing factors. 

The American College of Obstetricians and Gynecologists (ACOG) has found that oral estrogen therapies may increase the risk of blood clots more than patches placed on the skin. ACOG recommends patients discuss the risks and benefits with their doctor prior to starting estrogen therapy.

3. Cancer and cancer treatment.

The CDC estimates that as many as 1 in 5 blood clots are related to cancer or cancer treatment. The risk is greatest shortly after diagnosis when patients typically undergo cancer treatment. 

Cancers of the brain, lungs, pancreas, stomach, kidneys, blood, and female reproductive organs tend to be the highest risk, as are advanced stage cancers. Patients who need hospitalization, surgery, catheterization, hormone therapy, or chemotherapy are at increased risk.

Talk with your doctor if you are preparing to start cancer treatment and have other risk factors for blood clots. Your care team will work with you to tailor a treatment plan that factors in your risks.

4. Genetic hypercoagulable conditions.

Studies show that more than 80% of patients with a thrombus have a blood or genetic disease that increased their risk. What’s more, approximately 7% of patients with DVTs have a genetic abnormality. 

Patients may need to be evaluated for inherited and acquired hypercoagulable conditions if they develop recurrent clots, multiple clots, or clots in unusual places. Many of these conditions are treatable with specialized, expert care and anticoagulant medicines. 

5. Obesity.

Obese patients are at increased risk of developing many health conditions, including blood clots. Studies have shown that adult patients with elevated body mass index (BMI) are more likely to develop recurring clots than patients who maintain a healthy weight. Generally, patients with a BMI of 25.0 to 29.9 are considered to be overweight, while a BMI over 30 indicates obesity. BMI is calculated by dividing a patient’s weight in kilograms by their height in meters squared.

According to the American Heart Association, overweight children have just as much of an increased risk of
developing blood clots as adults. A 2019 study of more than 300,000 children found those with higher BMI had the highest risk of developing serious clots later in life. While an estimated 13.7 million children and adolescents in the United States are obese, the study also found that kids whose BMI fell below 25 by age 13 showed no increased risk of blood clots as adults.

Your doctor can help you or your child achieve a healthy weight. Our experts can work with you to make nutritious food choices, incorporate regular exercise as a part of your routine, and prescribe medications to help control underlying health problems that contribute to obesity, such as metabolic disease and Type 2 diabetes. 


6. Leading a sedentary lifestyle.

Limited mobility increases the risk of several health problems, including obesity and Type 2 diabetes. Clots are no exception, and the COVID-19 pandemic has led many people to become more sedentary.

The good news is the effects of a sedentary lifestyle can be countered. If you work at a desk, consider the tips below to help reduce your risk.

  • Stand up from your desk and take regular breaks. These so-called “microbreaks” can aid circulation and even reduce stress.
  • Talk with your doctor about a plan to achieve an optimal weight. Losing excess weight can give you more energy to stay active as well as reducing weight-related blood clot risk factors.
  • Drink an adequate amount of water. How much water you should drink depends upon your age, sex, and other factors. About a half-gallon per day (or 8 glasses of 8 ounces each) is a good place to start. 

Some research suggests that long-distance travel (six hours or more seated) may lead to increased risk of developing a clot, but other studies have contradicted these findings. Generally, try to break up long periods of sitting with stretching and moving about. If you have other risk factors for thrombus, be sure to talk with your doctor about specific travel precautions. 

7. Recent orthopedic surgery.

Patients who have had orthopedic surgery are often at risk of developing a thrombus due to the necessity of immobility after complex procedures such as joint replacement. The American Joint Replacement Registry notes that in 2019, Orthopedic surgeons performed about 1.5 million hip and knee replacements. 

Serious blood clots are widely recognized as a major risk for patients undergoing hip and knee replacement surgery. According to The National Blood Clot Alliance, without preventative treatment, as many as 80% of patients could develop a DVT after orthopedic surgery, and 10-20% could develop a PE. Even when preventative measures are taken, clots account for the most common cause of emergency re-admission to the hospital and death following joint replacement surgeries. 

Hospitalized patients, especially those in the intensive care unit, often receive DVT prophylaxis in the form of an injection or oral blood thinners. Patients who are immobilized may require an extended course of blood thinning medications, which may be oral pills or injections. 

Once patients can move more, the risk of developing a blood clot is significantly lower. That’s why doctors remind patients who are going home from the hospital to stay active and hydrated. Some patients, depending on their age and mobility, may need to remain on a lower dose of blood thinning medication during recovery and rehabilitation.

Are you at risk for a serious blood clot?

Discuss your risk factors with your doctor.

Call 202-877-DOCS (3627) or Request an Appointment


Diagnosis and treatment options.

While clots are traditionally treated with blood thinners like coumadin and warfarin, a new group of medications called direct oral anticoagulants (DOACs) has become available in the last decade. 

These medications are groundbreaking for patients. Unlike traditional blood thinners, DOACs don’t require the same sorts of blood tests or food limitations and are highly effective at preventing dangerous clots with few side effects. Traditional blood thinners can cause interactions with some antibiotics, common over the counter medications, alcohol, and foods that contain vitamin K, such as leafy green vegetables.

Blood thinners can also come with a host of negative side effects related to risk of bleeding. These include but are not limited to:

  • Dizziness
  • Red or brown urine
  • Severe headache or stomach pain
  • Vomiting of blood
  • Vison changes

MedStar Health is involved in research of effectiveness of DOACs including use of these agents in “special populations,” including patients with cancer, those on dialysis with end stage kidney disease, and obese patients. Early results suggest the drugs are safe and effective for these patients, who have historically been treated with older blood thinners. 

Thanks to the research being conducted at MedStar Health and elsewhere, DOACs are proving to be useful for doctors in treating clotting in many different types of patients. These drugs are reducing hospital stays and improving postoperative outcomes.

Other common medications are administered via injection one or two times per day. These heparin-based medicines are considered safest for pregnant patients. Like other anticoagulants, heparin decreases the blood’s ability to form clots. 

However, coumadin and warfarin are the best option for some patients, such as those with a mechanical heart valve and pregnant patients. Be sure to talk with your doctor before starting any medication.

March is Clot Awareness Month.

Each March, the National Blood Clot Alliance (NBCA) celebrates Clot Awareness Month. In hopes of helping more people understand the warning signs of blood clots, NBCA has launched a Stop the Clot website. This patient-focused site provides detailed information about blood clots risks and prevention, as well education, support, and materials for patients recovering from a clot. 

Serious blood clots are a life-threatening emergency. Being aware of the warning signs and reducing risks can go a long way toward avoiding hospitalization, and modern drugs are helping prevent clots after surgery. With knowledge and excellent care, blood clots can be prevented and treated. 

For more information about how you can avoid a serious blood clot and improve your health, talk with your doctor.

Are you or a loved one concerned about developing a blood clot?

Our experts are here to help.

Call 202-877-DOCS (3627) or Request an Appointment

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