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Ask the Doc: Why Does One Leg Swell More Than the Other? With Dr. Adeeb Sebai

MAY 4, 2026

Welcome back to Ask the Doc, an educational series from United Vein & Vascular Centers designed to provide clear, physician-led answers to common questions about vein and vascular health. Each week, a UVVC physician explains everyday symptoms and what they may mean medically.

In this installment, Dr. Sebai addresses a symptom that often raises concern for patients:

“Why does one leg swell more than the other?”

Q: What are the common causes of one-sided leg swelling?

Dr. Sebai:

Swelling in one leg can occur for a variety of reasons, and identifying the cause is key to proper treatment. Some of the most common causes include:

  • Injury or inflammation in the affected leg
  • Infection in the skin or underlying tissue
  • Lymphatic system issues, such as lymphedema
  • Vein-related conditions affecting blood flow
  • Permanencia prolongada de pie o sentado

While some causes may be temporary, persistent swelling should always be evaluated.

A woman's legs are shown with large swollen veins on the left leg

Q: When does swelling indicate a circulation problem?

Dr. Sebai:

One-sided swelling is often linked to circulation issues, particularly when blood is not moving efficiently through the veins.

When veins are not functioning properly, blood can pool in the affected leg. This increases pressure and can cause fluid to leak into surrounding tissues, leading to noticeable swelling, especially by the end of the day or after long periods of standing.

Q: Could swelling in one leg be a blood clot?

Dr. Sebai:

In some cases, swelling in one leg may be caused by a blood clot, also known as deep vein thrombosis (DVT). This occurs when a clot forms in a deep vein, usually in the leg.

Signs that may suggest a clot include:

  • Sudden swelling in one leg
  • Pain or tenderness
  • Calor en la zona afectada
  • Redness or discoloration

Because DVT can lead to serious complications, sudden or unexplained swelling should be evaluated promptly.

Q: How does vein disease contribute to swelling?

Dr. Sebai:

Vein disease, particularly chronic venous insufficiency (CVI), is a common cause of leg swelling. This condition occurs when vein valves do not work properly, allowing blood to flow backward and pool in the legs.

Over time, this increased pressure can lead to:

  • Swelling in one or both legs
  • Heaviness or fatigue
  • Skin changes or discoloration
  • Varices visibles

While CVI often affects both legs, it may begin or appear more noticeable on one side.

Q: When should someone seek medical attention?

Dr. Sebai:

You should consider seeking medical care if one leg is consistently more swollen than the other, if swelling appears suddenly or worsens quickly, or if it is accompanied by pain, warmth, or redness. Swelling that does not improve with rest or elevation, or symptoms that begin to interfere with walking or daily activities, should also be evaluated.

A vein specialist can assess your symptoms and may use imaging tests, such as a duplex ultrasound, to determine the underlying cause.

Preguntas frecuentes

Is swelling in one leg dangerous?

It can be. While some causes are minor, swelling in one leg may also indicate a more serious condition such as a blood clot or circulation issue.

Can dehydration cause swelling?

Dehydration is not a common direct cause of swelling. Swelling is more often related to circulation, fluid balance, or underlying medical conditions.

What tests diagnose swelling causes?

Duplex ultrasound is commonly used to evaluate blood flow in the veins and check for clots or valve dysfunction.

When should I go to the doctor?

You should seek evaluation if swelling is persistent, sudden, or accompanied by pain, redness, or warmth.

Can vein disease cause swelling in one leg?

Yes. Vein disease can affect one leg more than the other, especially in the early stages or when circulation is uneven.

What’s Next in the Ask the Doc Series

Swelling in one leg can have many causes, and understanding the difference is key to getting the right care. The Ask the Doc series continues to explore how symptoms related to circulation and vein health can appear in different ways.

In our next installment, Dr. Robert Osipov will address another common question: why do my ankles swell more in warm weather? He’ll explain how heat can affect circulation, why swelling may become more noticeable during warmer months, and when it may be a sign of an underlying vein condition.

If one leg is consistently swollen, schedule a consultation to determine the cause. You can find a United Vein & Vascular Centers clinic near you and connect with a specialist for evaluation.

Si le preocupa la salud de sus venas, programe una consulta con un especialista en venas y vasos sanguíneos para tranquilizarse.

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