What Causes Varicose Veins?

Varicose veins are the enlarged, twisted, rope-like veins that most often appear on the legs. Understanding what causes varicose veins starts with how healthy veins are supposed to work — and what happens when that system breaks down.

How Healthy Veins Work

Your leg veins carry blood back up to your heart against gravity. To do this, they rely on a series of one-way valves that open to let blood flow upward and close to stop it from flowing backward. The muscles in your calves act like a pump, squeezing the veins each time you move and helping push blood along.

What Causes Varicose Veins to Form

Varicose veins develop when these valves weaken or become damaged. When a valve doesn't close properly, blood can flow backward and pool in the vein, a process called venous reflux. Over time, the pooled blood increases pressure inside the vein, causing it to stretch, bulge, and twist under the skin.

Genetics

A family history of varicose veins is one of the strongest predictors of whether you'll develop them yourself. Inherited traits can affect the strength and structure of vein walls and valves.

Age

Veins naturally lose some elasticity over time, and valves can wear down with years of use, making varicose veins more common as people get older.

Prolonged Standing or Sitting

Jobs or habits that involve long periods without movement reduce the effectiveness of the calf muscle pump, allowing blood to pool in the lower legs.

Pregnancy and Hormonal Changes

Increased blood volume, hormonal shifts, and pressure from a growing uterus can all contribute to varicose veins during and after pregnancy.

Excess Weight

Carrying extra body weight increases pressure on the veins in the legs and pelvis, adding strain to already-working valves.

Sex and Hormonal Factors

Varicose veins are more commonly reported in women, which researchers link in part to hormonal factors that can affect vein wall relaxation.

Managing Your Risk

While you can't change your genetics or age, understanding the causes of varicose veins can help you focus on the factors you can influence — staying active, managing your weight, taking movement breaks, and wearing supportive compression when needed.

Graduated Compression Stockings

Because prolonged standing and sitting are among the most controllable contributors to varicose veins, many people build graduated compression stockings into their daily routine to support circulation.

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Other Contributing Factors

Previous Blood Clots or Vein Injury

Damage to a vein from a past blood clot or injury can affect how well its valves function afterward, sometimes contributing to varicose veins in that area.

Abdominal Pressure

Chronic constipation, persistent coughing, or other sources of increased abdominal pressure can add strain to the venous system over time, making valve failure somewhat more likely in susceptible people.

Lack of Movement

Beyond occupational standing or sitting, a generally sedentary lifestyle reduces how often your calf muscle pump is activated, which can allow blood to pool more easily during the day.

Why Understanding the Cause Matters

Knowing what causes varicose veins helps set realistic expectations for both prevention and treatment. Since valve damage doesn't reverse itself, lifestyle habits are generally aimed at slowing progression and easing symptoms rather than eliminating existing varicose veins — for veins you'd like removed or closed, a medical procedure is typically required. Our guide to non-surgical treatment options covers what that process generally involves.

When Varicose Veins Need Medical Attention

Most varicose veins are a cosmetic and comfort issue, but if you notice skin changes, persistent pain, swelling, or sores near a varicose vein, it's worth discussing with a healthcare provider.

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