Leg pain, swelling, warmth, or visible veins can be concerning, especially when you are unsure whether the problem is a varicose vein or a blood clot.

Although varicose veins and deep vein thrombosis (DVT) both affect the veins, they are very different conditions. Varicose veins develop in veins near the skin’s surface and are often visible. A DVT is a blood clot that forms in a vein deep inside the body, most commonly in the calf or thigh.

Knowing the differences, and recognizing when symptoms require urgent medical attention, can help you take the appropriate next step.

What Are Varicose Veins?

Varicose veins are enlarged, twisted veins that typically appear blue or purple beneath the skin. They develop when valves inside the veins weaken or become damaged.

Healthy vein valves help move blood from the legs back toward the heart. When those valves do not close properly, blood can flow backward and collect in the vein. This condition is known as venous reflux. Over time, the increased pressure can cause the vein to stretch, bulge, and become visible.

Varicose veins frequently develop gradually and may affect one or both legs.

Common symptoms include:

• Bulging or twisted surface veins
• Aching, throbbing, or burning
• Tired or heavy-feeling legs
• Mild ankle or lower-leg swelling
• Itching around the affected veins
• Leg cramps, especially at night
• Symptoms that worsen after prolonged standing or sitting
• Skin discoloration near the ankle

Varicose veins are not always simply a cosmetic concern. Without appropriate care, chronic venous disease may progress and contribute to inflammation, skin changes, bleeding, or venous ulcers.

What Is Deep Vein Thrombosis?

Deep vein thrombosis occurs when a blood clot forms in one of the body’s deep veins. DVT most often develops in the lower leg, thigh, or pelvis.

Unlike a varicose vein, a DVT usually cannot be seen from outside the body. Symptoms may develop suddenly, although some people with DVT have few or no noticeable symptoms.

Possible warning signs include:

• Sudden swelling, usually in one leg
• Calf or thigh pain or tenderness
• A feeling of tightness in the leg
• Warmth in the affected area
• Red or discolored skin
• Unexplained pain that may become worse when standing or walking

A DVT requires prompt medical evaluation because part of the clot can break away and travel through the bloodstream to the lungs. This is called a pulmonary embolism, or PE, and it can be life-threatening.

Varicose Veins and DVT: A Side-by-Side Comparison

Can Varicose Veins Cause a DVT?

A visible varicose vein is not the same thing as a DVT, and a varicose vein does not simply “turn into” a deep vein blood clot.

However, varicose veins can sometimes develop a clot in a vein near the skin. This is known as superficial venous thrombosis or superficial thrombophlebitis. It may cause a tender, red, warm, or firm area along the path of the vein.

Although this condition is different from DVT, it should still be evaluated. In certain cases, a superficial clot can extend toward the deep venous system. An ultrasound may be recommended to determine the clot’s location and extent.

Who Is More Likely to Develop Varicose Veins?

Factors that can increase the likelihood of varicose veins include:

• A family history of vein problems
• Increasing age
• Pregnancy
• Being overweight or obese
• Spending long periods standing or sitting
• Previous leg injury or blood clot
• Hormonal changes
• Limited physical activity

Varicose veins are common, but persistent symptoms should not be ignored—particularly when swelling, skin discoloration, inflammation, or wounds are present.

What Increases the Risk of DVT?

A DVT can affect almost anyone, but certain circumstances raise the risk. These include:

• Recent surgery, hospitalization, or injury
• Prolonged immobility or bed rest
• Long-distance travel
• Cancer and some cancer treatments
• Pregnancy and the postpartum period
• Estrogen-containing medications
• A previous DVT or pulmonary embolism
• An inherited clotting disorder
• A family history of blood clots
• Increasing age
• Obesity

Having more than one risk factor can further increase the likelihood of developing a clot. The CDC provides additional information about DVT and pulmonary embolism risk factors.

How Are Vein Problems Diagnosed?

Because several conditions can cause leg pain and swelling, symptoms alone cannot reliably confirm or exclude a DVT. A medical evaluation is necessary.

A venous duplex ultrasound is a noninvasive test that uses sound waves to examine the veins and evaluate blood flow. The type of ultrasound performed depends on the suspected problem.

For varicose veins, an ultrasound may look for venous reflux and identify valves that are not functioning properly. When a DVT is suspected, ultrasound is used to look for evidence of a clot and determine whether blood is moving normally through the deep veins.

When Should You Seek Urgent Medical Care?

Seek prompt medical evaluation if you experience sudden swelling in one leg, unexplained calf or thigh pain, warmth, redness, or skin discoloration—especially when symptoms occur after surgery, hospitalization, prolonged travel, or a period of limited mobility.

Call 911 or seek emergency care immediately if you develop possible symptoms of a pulmonary embolism, including:

• Sudden shortness of breath
• Chest pain, particularly pain that worsens when breathing deeply or coughing
• A rapid or irregular heartbeat
• Coughing up blood
• Lightheadedness or fainting

These symptoms should never be treated as a routine varicose vein problem. According to the CDC, a pulmonary embolism can occur when part of a deep vein clot travels to the lungs and blocks blood flow.

Do Not Guess About New Leg Symptoms

Visible varicose veins generally develop gradually and cause aching, heaviness, itching, or discomfort that becomes more noticeable after standing. A DVT is more likely to cause sudden, one-sided swelling, pain, tenderness, or warmth, but symptoms can overlap, and some blood clots produce no obvious warning signs.

If you are experiencing new or unexplained leg symptoms, an appropriate medical evaluation can help identify the cause and determine whether routine vein care or urgent treatment is needed.

The vascular specialists at the Vein Institute of New Jersey evaluate and treat a full range of venous conditions, from symptomatic varicose veins to more complex circulation problems.

To schedule a vein evaluation, call 973-539-6900 or visit VeinInstituteNJ.com.

This article is intended for educational purposes and should not replace professional medical advice, diagnosis, or emergency care.