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Causes - Varicose veins

Varicose veins are usually caused by weak vein walls and valves.

Inside your veins are tiny one-way valves. These open to let the blood through. They then close to prevent it from flowing backwards.

Sometimes the walls of the veins become stretched and lose their elasticity. This causes the valves to weaken.

If the valves don't function as they should, this can cause the blood to leak and flow backwards. If this happens, the blood collects in your veins, which become swollen and enlarged.

We don't know why the walls of the veins stretch and the valves in your veins weaken. Some people develop the condition for no clear reason.

Increased risk

Your likelihood of developing varicose veins can increase if you:

  • are female
  • have a close family member with varicose veins
  • are elderly
  • are overweight
  • have a job that involves long periods of standing
  • are pregnant
  • have other conditions


Women are more likely to get varicose veins than men. This may be because female hormones tend to relax the walls of veins. This makes the valves more prone to leaking.

Hormones are chemicals produced by the body.

Changes may happen because of:

  • pregnancy
  • premenstrual syndrome 


Your risk of developing varicose veins is higher if a close family member has the condition.

Varicose veins may be inherited. They may be partly caused by your genes.


As you get older, your veins start to lose their elasticity. The valves inside them stop working as well.

Being overweight

Being overweight puts extra pressure on your veins which means they have to work harder to send the blood back to your heart.

This can put increased pressure on the valves and makes them more prone to leaking.

The impact of body weight on varicose veins appears to be more significant in women.

Use the healthy weight BMI calculator - to check if you're overweight.

Your job

If you have a job where you're standing for long periods, you may have a higher risk of getting varicose veins.

This is because your blood doesn't flow as easily when you're standing for a long time.


During pregnancy, the amount of blood increases to help support the developing baby. This puts extra strain on your veins.

Increased hormone levels also cause the walls of the blood vessels to relax. This also increases your risk.

Varicose veins may also develop as the womb (uterus) begins to grow. As the womb expands it puts pressure on veins in your pelvic area. This can sometimes cause them to become varicose.

Being pregnant can increase your risk. But most women find their veins improve after the baby is born.

Other health conditions

In rare cases, other health conditions cause varicose veins.

These include:

  • a previous blood clot
  • a swelling or tumour in the pelvis
  • abnormal blood vessels
  • a history of leg injury (for example, having previously broken a bone in your leg)

Preventing varicose veins

There's very little evidence to suggest you can:

  • stop varicose veins getting worse
  • completely prevent new ones developing

But there are ways to ease symptoms of existing varicose veins.

These include:

  • avoiding standing or sitting still for long periods – try move around every 30 minutes
  • taking regular breaks throughout the day – raise your legs on pillows while resting. This can ease discomfort
  • exercising – this can improve circulation and help maintain a healthy weight

Read about diagnosing varicose veins

Content supplied by the NHS and adapted for Ireland by the HSE

Page last reviewed: 25 March 2021
Next review due: 25 March 2024

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.