Blood Home > Cause of Varicose Veins

A weakening of one-way valves within the veins is the primary cause of varicose veins. When these valves weaken, blood can leak back in the vein, collecting there and enlarging the vein. Risk factors, while not a direct cause, can increase a person's chances of developing varicose veins. These risk factors include increased age, a family history of vein problems, obesity, and pregnancy.

What Causes Varicose Veins?

The cause of varicose veins is weakening of the valves within the veins. To understand this, it may be helpful to understand what veins do.
Veins are a type of blood vessel. They are responsible for carrying blood from the body back to the heart. To make sure that blood gets back to the heart, veins have valves that act as one-way flaps. These valves prevent the blood from flowing backwards. If the one-way valves become weak, blood can leak back into the vein and collect there. This problem is called venous insufficiency. Pooled blood enlarges the vein and it becomes a varicose vein.

Know the Risk Factors for Varicose Veins

While not causes of varicose veins, a number of factors can increase a person's chances for developing weakened valves. These are known as varicose vein risk factors. The more risk factors a person has, the greater their chances for developing the condition.
Risk factors include:
  • Increasing age.
  • Having family members with vein problems or being born with weak vein valves.
  • Hormonal changes that occur during puberty, pregnancy, and menopause. Taking birth control pills and other medicines containing estrogen and progesterone also increases the risk of varicose veins.
  • Pregnancy. During pregnancy, there is a huge increase in the amount of blood in the body, which can cause veins to enlarge. The expanding uterus also puts pressure on the veins. Varicose veins usually improve within three months after delivery. A growing number of abnormal veins usually appear with each additional pregnancy.
  • Obesity, leg injury, prolonged standing, and other things that weaken vein valves.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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