What Causes Varicose Veins?
Medically verified
Last updated on 1/29/2026

By Dr. Michael Nguyen
Vein Doctor at Vein Treatment Clinic
Harvard Medical School
Board Certified by the American Board of Venous and Lymphatic Medicine
Estas venas várices develop when the veins in the legs cannot move blood efficiently back toward the heart. Increased pressure builds inside the vein, causing it to enlarge, twist, and become visible beneath the skin.
When patients ask what causes varicose veins in the legs, the answer usually involves a combination of valve failure, genetics, aging, pregnancy, and prolonged standing. Understanding the causes of varicose veins and their risk factors helps explain why they form and why some people are more likely to develop them.

Understanding why varicosas forms helps patients recognize risk factors, anticipate progression, and decide when evaluation or treatment may be helpful.
If you’re unsure which factors may be contributing to your veins, a vein evaluation can help clarify the cause.
Valve failure inside the veins
The most common cause of varicose veins is failure of the one way valves inside the leg veins. These valves normally keep blood moving upward toward the heart, which may raise the question. Are they dangerous? These valves normally keep blood moving upward toward the heart.
When valves weaken or stop closing properly, blood flows backward and pools in the vein, increasing pressure and stretching the vein walls. This valve dysfunction is the primary reason varicose veins form.

Healthy vs. damaged vein valves.

Healthy vs. damaged vein valves
Genetics and family history
Genetics play a major role in why varicose veins form especially in families with inherited valve weakness. People with close family members who have varicose veins are more likely to develop them.
Inherited vein wall weakness or valve structure increases susceptibility, even in otherwise healthy individuals.
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Why varicose veins are more common with age
Aging and varicose veins are closely linked. As people age, vein walls lose elasticity and valve function can decline.
These age related changes increase the likelihood of blood pooling and visible vein enlargement over time.
Pregnancy and hormonal changes
Pregnancy and varicose veins are commonly associated due to increased blood volume, hormonal changes, and added pressure on the leg veins.
Hormones relax vein walls, making valve failure more likely. While some veins improve after pregnancy, underlying valve damage can persist.
Temporary Change or Lasting Issue? Learn How Pregnancy Affects Your Vein Health
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Prolonged standing or sitting
Prolonged standing causes varicose veins to worsen by reducing the muscle pumping action that helps move blood upward.
Over time, standing for long periods increases vein pressure and accelerates valve dysfunction, especially in individuals with existing risk factors.
Excess weight and increased vein pressure
Additional body weight increases pressure on the veins in the legs, making it harder for blood to return to the heart.
While weight alone does not cause varicose veins, it can worsen existing vein disease.
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Table of contents
1. Valve failure inside the veins
2. Genetics and family history
3. Why varicose veins are more common with age
4. Pregnancy and hormonal changes
5. Prolonged standing or sitting
6. Excess weight and increased vein pressure
7. Previous blood clots or vein injury
8. Do lifestyle factors cause varicose veins?
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Previous blood clots or vein injury
This damage increases the risk of developing varicose veins later on.
Do lifestyle factors cause varicose veins?
Lifestyle factors such as inactivity, prolonged immobility, and excess weight contribute to increased vein pressure and symptom progression.
While these factors influence how varicose veins develop, they typically act in combination with underlying valve weakness rather than serving as the sole cause.
Lifestyle changes may reduce symptoms but do not reverse valve damage once it has occurred.
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Vein Treatment Clinic is powered by VIP Medical Group and built around a single guiding principle: deliver the highest standard of vein care using an academic, evidence-based approach combined with the most advanced, minimally invasive technology available today.
Clinical leadership at Vein Treatment Clinic is guided by a panel of board-certified vein specialists responsible for establishing and maintaining the clinic’s medical standards. Their approach reflects training and experience developed at nationally recognized academic institutions such as Harvard, Yale, Columbia, and Mount Sinai, with a focus on disciplined evaluation, accuracy, and outcomes-driven care.
All physicians at Vein Treatment Clinic follow a structured, highly standardized clinical model. This includes ongoing training in the latest non-surgical vein treatments, continuous review of emerging research, and strict adherence to proven safety and quality protocols. The approach reflects the values of academic medicine: thoughtful evaluation, disciplined decision-making, and a commitment to outcomes grounded in science.

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