Deep vein thrombosis refers to the formation of a blood clot in a vein deep underneath your skin. Typically, deep vein thrombosis, or DVT, occurs in veins in the legs. Because DVT is a serious condition that requires urgent treatment, it is important to know your risk and to seek vein treatment in Houston as soon as possible if you recognize the symptoms. Without treatment, a blood clot in your leg could break off and travel to your lungs, where it causes a life-threatening blockage.
Quick Answer: Your risk of deep vein thrombosis (DVT) rises when blood flow slows, the vein wall is injured, or the blood clots more easily than normal. The biggest triggers are recent surgery or hospitalization, long periods of immobility, cancer, pregnancy and the weeks after delivery, estrogen-containing medicines, a previous clot, inherited clotting disorders, obesity and older age. Risk adds up: two or three factors together matter far more than one. If you have sudden one-sided leg swelling, pain or warmth, get checked the same day.
There are several risk factors for DVT. You are more vulnerable to DVT if you have a clotting disorder or if you have recently had surgery during which your veins may have been injured. Smoking and birth control pills increase the risk for DVT, and those with heart failure, some forms of cancer, inflammatory bowel disease, or a family history of blood clots are also more likely to experience DVT. Inactivity is a major DVT risk factor. For instance, sitting for extended periods on airplanes or during car trips, or being on prolonged bed rest can put you at risk.
Meet your vein specialist
Dr. Syed Raza, MD
Vascular & Interventional Radiology · Founder, Premier Vein & Vascular Center
Fellowship-trained interventional radiologist certified by the American Board of Radiology and the Royal College of Radiologists (UK). Former Chief of Interventional Radiology at UTMB Galveston and Memorial Hermann Memorial City, with 15+ years treating varicose veins, venous reflux and peripheral arterial disease.
Why Some People Are at Higher Risk of Deep Vein Thrombosis
More than 150 years ago, the pathologist Rudolf Virchow described three conditions that make a blood clot likely. Doctors still use his framework, known as Virchow’s triad, because nearly every DVT risk factor fits into one of its three parts:
- Slow blood flow (stasis). When the leg muscles are not moving, blood in the deep veins slows and can pool, especially behind the valves. Long flights, bed rest, a leg cast or paralysis all create stasis.
- Injury to the vein wall. Surgery, fractures, a central line or catheter, or trauma can damage the inner lining of a vein, which triggers the clotting process at that spot.
- Blood that clots too easily (hypercoagulability). Cancer, pregnancy, estrogen, certain inherited conditions and some inflammatory diseases tip the chemistry of the blood toward clotting.
A single factor may only raise risk slightly. Problems usually arise when several overlap, for example a person who has hip surgery, then spends days mostly in bed, while also taking hormone therapy. Understanding which factors apply to you helps you and your doctors decide on sensible prevention.
DVT Risk Factors at a Glance
The original article above lists the common risk factors. The table below groups them by how strongly they tend to raise risk and how long that risk lasts, which is how doctors think about prevention.
| Risk factor | Relative strength | How long risk lasts | Common prevention approach |
|---|---|---|---|
| Major orthopedic surgery (hip, knee replacement) | High | Several weeks after surgery | Blood thinner prescribed by surgeon, early walking, compression devices |
| Hospital stay or bed rest | Moderate to high | While immobile and shortly after | Moving the legs, early walking, medication when indicated |
| Active cancer and chemotherapy | High | Throughout treatment | Individual assessment by the oncology team |
| Previous DVT or pulmonary embolism | High | Lifelong | Discuss extended anticoagulation and high-risk situations with your doctor |
| Pregnancy and the 6 weeks after delivery | Moderate | Pregnancy through postpartum period | Staying active; medication in selected high-risk women |
| Estrogen birth control or hormone therapy | Mild to moderate | While taking it | Review options if other risk factors are present |
| Long-distance travel over 4 hours | Mild | During and shortly after the trip | Move every hour, calf exercises, fluids, compression socks if advised |
| Obesity, smoking, older age | Mild to moderate | Ongoing | Weight management, quitting smoking, staying active |
Situations That Temporarily Raise Your Risk
Surgery and hospitalization
Surgery is one of the strongest triggers. Operations on the hip, knee, pelvis and abdomen, and longer operations under general anesthesia, carry the highest risk. Being in the hospital for any serious illness adds to it, because people move far less than usual. Hospitals routinely assess clot risk for this reason, and many patients go home with instructions for blood thinners or compression. Following those instructions, even when you feel fine, is important.
Injuries and casts
A broken leg or ankle, especially when it requires a cast or boot that keeps the calf muscles from working, slows flow in the deep veins. Ask your orthopedic team whether you need clot prevention while your leg is immobilized.
Pregnancy and after delivery
During pregnancy the blood naturally becomes more prone to clotting, which protects against bleeding at delivery. The growing uterus also presses on the pelvic veins. The risk remains raised for about six weeks after birth and is higher after a cesarean section. Pain or swelling in one leg during this time should never be dismissed as normal pregnancy swelling.
Travel
Sitting in a cramped seat for hours keeps the calf pump idle. For healthy people the added risk is small, but it becomes meaningful when combined with other factors such as recent surgery, pregnancy or a past clot. Getting up to walk, flexing your ankles and staying hydrated all help.
Long-Term and Inherited Risk Factors
Some risk factors are present for years or for life. These include a previous DVT or pulmonary embolism, inherited clotting conditions such as factor V Leiden or prothrombin gene mutation, antiphospholipid syndrome, active cancer, heart failure, inflammatory bowel disease, kidney disease with protein loss, obesity and older age, with risk climbing steadily after 60.
A family history of clots is worth mentioning to every doctor who treats you, particularly before surgery, pregnancy or starting estrogen. In some families, blood testing for inherited conditions is appropriate, though it does not always change management and should be guided by a specialist.
Do varicose veins raise the risk of DVT?
Varicose veins are a superficial vein problem, while DVT occurs in the deep veins. Even so, people with significant varicose veins appear to have a modestly higher chance of developing DVT, and inflamed, clotted surface veins (superficial thrombophlebitis) can sometimes extend into the deep system. If a varicose vein becomes hard, red and tender, have it checked with an ultrasound. Our varicose vein treatment page explains how these veins are evaluated and managed.
Recognizing the Symptoms of DVT
Knowing your risk is only useful if you also know what a clot can feel like. DVT usually affects one leg, not both. Common signs include:
- Swelling of one calf, ankle or the whole leg
- Pain or tenderness, often described as a cramp or a pulled muscle that does not ease
- Warmth over the affected area
- Red, purple or darker skin compared with the other leg
- Surface veins that look more prominent than usual
Some clots cause very few symptoms, which is why people at high risk sometimes need preventive treatment even when they feel well. A clot can also form in an arm, particularly in people with a central line, port or catheter.
Call 911 or go to the emergency room if you have:
- Sudden shortness of breath or rapid breathing
- Chest pain that is sharp and worse when you breathe in or cough
- Coughing up blood
- A racing heartbeat, lightheadedness or fainting
These can be signs of a pulmonary embolism, which is a medical emergency. New swelling and pain in one leg without these symptoms still needs same-day medical evaluation.
How We Evaluate DVT Risk and Suspected Clots
At Premier Vein & Vascular Center, the evaluation focuses on two questions: is there a clot now, and what is your ongoing risk?
- Focused history. We ask about recent surgery, travel, illness, hormones, pregnancy, previous clots and family history, and when your leg symptoms began.
- Examination. We compare both legs for swelling, tenderness, color change and visible veins, and check the pulses.
- Venous duplex ultrasound. This painless scan in our IAC-accredited vascular lab is the standard test for DVT. It shows whether the deep veins compress normally and whether clot is present, and it also looks for reflux or old scarring from previous clots.
- A clear plan. If a clot is found, we start or coordinate treatment promptly. If there is no clot, we explain what is causing your symptoms and discuss practical prevention for your situation.
How DVT Is Treated
Most DVTs are treated with anticoagulant medicines, often called blood thinners. These do not dissolve the existing clot directly, but they stop it from growing and lower the risk of a new clot or a pulmonary embolism while the body gradually breaks the clot down. Treatment typically lasts at least three months, and longer in some situations.
For large clots in the thigh or pelvic veins that cause severe swelling, interventional radiologists may use catheter-based techniques to remove or break up the clot. Compression and walking, once cleared by your doctor, help with swelling. You can learn more on our deep vein thrombosis treatment page.
Why follow-up matters after a clot
A DVT can damage the valves inside the deep veins. Months or years later, some patients develop post-thrombotic syndrome, with chronic swelling, heaviness, skin darkening and sometimes ulcers. Ongoing follow-up, compression when advised and treatment of any related superficial vein reflux can help limit these long-term effects.
Practical Ways to Lower Your DVT Risk
- Walk as soon as it is safe after surgery or illness, and follow any prevention plan you are given
- On trips longer than about four hours, get up every hour or two and flex your ankles often while seated
- Drink enough water and limit alcohol when traveling
- Do not smoke, and work toward a healthy weight
- Tell your doctor about any previous clot or family history before surgery, pregnancy or starting hormones
- Ask whether compression stockings are appropriate for you during travel or recovery
- Take blood thinners exactly as prescribed and do not stop them without talking to your doctor
Questions to ask before surgery, pregnancy or a long trip
Patients often tell us they never thought to ask about clots until they had one. A few minutes of conversation beforehand can make a real difference, so consider asking your doctor or surgeon:
- What is my personal risk of a blood clot with this procedure or situation?
- Will I need a blood thinner, and for how long after I go home?
- Should I wear compression stockings or use calf compression devices, and when can I stop?
- How soon after surgery should I start walking, and how often?
- Do any of my current medications, including hormones, need to be paused?
- Which symptoms should make me call you or go to the emergency room?
If you have had a clot before, keep a short written summary of when it happened, where it was and how it was treated. Sharing that history with every new doctor helps them plan prevention properly. People who take long-term blood thinners should also let every provider, including dentists, know before any procedure, since doses sometimes need to be adjusted or timed carefully.
When to See a Vein Specialist in Houston
If you have several risk factors, a past clot, leg swelling that has not been explained, or symptoms after a recent surgery or long trip, an ultrasound evaluation gives clear answers. Dr. Syed Raza is a fellowship-trained interventional radiologist and former Chief of Interventional Radiology at UTMB Galveston and Memorial Hermann Memorial City. Our team can see you quickly as a Houston vein specialist, with same-week appointments usually available, and most insurance plans, including Medicare, are accepted. Remember that sudden breathing problems or chest pain always mean calling 911 first.
Talk With a Specialist at Premier Vein
Have questions about your symptoms or treatment options? Dr. Syed Raza and the team at Premier Vein & Vascular Center can evaluate your concerns and explain your options clearly. Same-week appointments are usually available, and most insurance plans are accepted.
Frequently Asked Questions
What is the most common cause of DVT?
The most common triggers are recent surgery, hospitalization and prolonged immobility, often combined with other factors such as cancer, older age or hormone use. In some people no clear trigger is found, which is called an unprovoked DVT.
Can young, healthy people get DVT?
Yes. Although risk increases with age, younger adults can develop DVT, especially with estrogen birth control, pregnancy, an inherited clotting disorder, a leg injury or a long period of immobility. One-sided leg swelling and pain should be checked regardless of age.
Does dehydration cause blood clots?
Dehydration is not a major cause on its own, but it may thicken the blood slightly and add to risk during long travel or illness. Drinking enough fluids is a sensible part of prevention, alongside moving your legs.
How is DVT diagnosed?
The standard test is a venous duplex ultrasound, which shows whether the deep veins compress normally and whether there is clot inside them. A blood test called a D-dimer is sometimes used first in an emergency setting to help rule out a clot.
Can a DVT go away on its own?
The body can slowly break down a clot, but an untreated DVT can grow or break loose and travel to the lungs. That is why DVT is treated with blood thinners and should never be left to resolve on its own.
Should I wear compression socks to prevent DVT?
Compression socks can help people at increased risk during long flights or recovery, but they are not a substitute for medication when a doctor prescribes it. People with significant artery disease should check with a doctor before wearing compression.
Trusted Health Resources
- Venous Thromboembolism, National Heart, Lung, and Blood Institute (NIH)
- About Venous Thromboembolism (Blood Clots), Centers for Disease Control and Prevention