What Causes Varicose Veins? Understanding the Risk Factors

Varicose veins develop when the one-way valves inside the leg veins become weakened or fail to close properly. This allows blood to flow backwards (venous reflux), increasing pressure within the superficial veins. Over time, the persistent pressure causes the veins to enlarge, become tortuous and visible beneath the skin.

Genetics — The Most Important Risk Factor

Family history is the strongest predictor of developing varicose veins. If one or both of your parents have varicose veins, your likelihood of developing the condition is significantly increased. Research suggests that inherited differences in the strength of the vein wall, connective tissue and vein valve function make some individuals more susceptible to venous reflux than others. This explains why many healthy, active people still develop varicose veins despite maintaining a healthy lifestyle.

Are Varicose Veins Hereditary?

Yes. Genetics is widely recognised as the single most important risk factor for developing primary varicose veins. If one or both of your parents have varicose veins, you are significantly more likely to develop them yourself. It is common for several members of the same family to be affected, often across multiple generations.

Researchers believe that inherited differences in the strength of the vein wall, connective tissue, and function of the one-way vein valves make some people more susceptible to developing venous reflux. These inherited traits mean that the valves are more likely to weaken over time, allowing blood to flow backwards and increasing pressure within the superficial veins.

This strong genetic influence explains why many people who are slim, physically active and otherwise healthy still develop varicose veins. Conversely, some individuals with recognised risk factors never develop the condition. While factors such as pregnancy, ageing, excess body weight and prolonged standing may contribute to disease progression or worsen symptoms, they are usually modifying factors rather than the underlying cause.

Although you cannot change your genetic makeup, adopting a healthy lifestyle — regular walking, maintaining a healthy weight, avoiding prolonged standing or sitting where possible, and staying physically active — can help reduce symptoms and support overall venous health.

If you have a strong family history and begin to notice leg aching, heaviness, swelling or visible varicose veins, it is worthwhile seeking assessment early. A duplex ultrasound scan can detect venous reflux before complications develop and help determine whether treatment is appropriate.

Ageing

As we age, the vein walls gradually lose elasticity and the valves may become less effective. This makes venous reflux more likely and explains why varicose veins become increasingly common with advancing age. However, younger adults — and occasionally even teenagers with a strong family history — can also develop varicose veins.

Pregnancy

Pregnancy is one of the most common triggers for varicose veins in women. Hormonal changes relax the vein walls, while the increased blood volume and pressure from the growing uterus make it more difficult for blood to return from the legs to the heart. The likelihood of developing varicose veins generally increases with each pregnancy, although some veins improve after childbirth.

Prolonged Standing or Sitting

Occupations that involve prolonged standing or sitting can worsen symptoms because the calf muscle pump is less effective when the legs remain still for long periods. This allows blood to pool within the leg veins, increasing venous pressure. While prolonged standing does not directly cause varicose veins in people with healthy vein valves, it may accelerate progression or make symptoms more noticeable in those who are already predisposed to venous disease.

Excess Body Weight

Being overweight or obese increases pressure within the veins of the legs and may contribute to worsening symptoms and progression of chronic venous disease. Maintaining a healthy body weight can help reduce symptoms, although it cannot reverse damaged vein valves.

Previous Deep Vein Thrombosis (DVT)

Some people develop varicose veins after a previous deep vein thrombosis. A blood clot can damage the valves within the deep veins, resulting in persistent venous hypertension and secondary venous reflux. This is known as post-thrombotic syndrome and requires specialist assessment because the pattern of venous disease may differ from primary varicose veins.

Can Varicose Veins Be Prevented?

Unfortunately, there is no guaranteed way to prevent varicose veins, particularly if they are inherited. However, regular walking, maintaining a healthy weight, avoiding prolonged periods of standing or sitting where possible, and staying physically active can help improve venous circulation and reduce symptoms.

Although lifestyle measures support overall vein health, they cannot repair faulty vein valves once venous reflux has developed. If symptoms persist or the veins are affecting your quality of life, a duplex ultrasound assessment by a vascular specialist can identify the underlying cause and determine whether treatment is appropriate.