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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
Varicose veins 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 varicose veins 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.
Does vein disease run in your family? Check Your Insurance Coverage
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.
Worried about weight-related vein pain? Consult an Expert Today
Before
After
A 37-year-old patient visited our Vein Treatment Clinic, seeking relief from unsightly and painful varicose and spider veins. We performed radiofrequency ablation and sclerotherapy treatments, significantly improving the veins’ appearance and completely eliminating discomfort. The patient is now enjoying a more active and pain-free lifestyle.
Before
After
A 69 year-old patient visited our California Vein Clinic, embarrassed by spider veins that had impacted their self-esteem. We performed radiofrequency ablation and sclerotherapy treatments, leaving their legs smooth and healthy. The patient now feels more confident, thanks to this transformative treatment.
Before
After
This 84 year-old patient at our New Jersey Vein Treatment Clinic came in with spider veins that had affected their daily routine. We used radiofrequency ablation and sclerotherapy treatments to relieve discomfort and restore both their leg health and confidence. The patient now enjoys a more active and fulfilling lifestyle, free from pain.
Before
After
At our Long Island Vein Clinic, we treated this 75 year-old patient with spider veins using radiofrequency ablation and sclerotherapy. These minimally invasive treatments improved both the patient’s appearance and overall well-being, offering transformative results.
Before
After
This 75 year-old patient visited our Long Island Vein Treatment Clinic with painful spider veins. We used radiofrequency ablation and sclerotherapy, minimally invasive treatments, to eliminate the veins and restore comfort and confidence. The patient experienced life-changing results
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.
Not sure which of these causes applies to your situation? Talk With a Vein Specialist