It’s normal for your penis to be veiny. In fact, these veins are important. After blood flows to the penis to give you an erection, the veins along your penis take blood back to the heart.

Some people have veins that are more visible than others. Vein size and shape can change over time or after having sex, getting injured, or having blood vessel surgery.

Read on to learn more about why your veins are important, how they can change over time, and when to see your doctor.

Ever notice how some people’s arm veins are more visible than others? This is influenced by many factors: the thickness of your skin, the size of the veins, and the level of activity you’ve recently engaged in. Penis vein visibility is influenced by many of the same factors.

When you get an erection, oxygenated blood from your heart travels through your arteries to three chambers of spongy tissue called the corpus cavernosum and the corpus spongiosum, to the shaft of your penis. The blood stays there until you’re no longer erect.

The blood then drains through the veins that run across the surface of your penis. This significant increase in blood flow can make the veins appear much larger than usual.

You may not see these veins when your penis is flaccid, because during this time very little blood is flowing through them.

The size of your veins has no impact on your ability to get or maintain an erection. Vein size doesn’t affect the strength or volume of your ejaculation, either.

Some conditions that impede blood flow, such as blood clots, can affect vein size and have some effects on erectile function.

Vein size can vary over time as a result of sexual activity or because of an underlying condition that affects penis blood flow.

Recent sexual activity

When you get an erection, about 130 milliliters (4.5 ounces) of blood flows to the spongy tissue inside the penis. The blood remains there, engorging the penis tissue, until you ejaculate or the erection goes away. The blood from the tissues then flows back to your heart through the veins in your penis, causing them to look more swollen than usual.

This is a normal part of getting an erection. Even if you normally don’t see veins on your penis when it’s flaccid, you may notice that the veins are more pronounced after you’ve masturbated or had sex. There’s no need to worry if your veins suddenly appear more swollen after increased sexual activity.

Varicocele

Varicocele are enlarged veins that can appear on your scrotum, giving them a veiny appearance. Varicocele are also called varicose veins, similar to the enlarged veins that often appear on your legs.

Varicocele usually appear when you’re a teenager. Around 10 to 15 of every 100 men have varicocele somewhere on their scrotum. They usually aren’t a cause for concern, and you likely won’t even notice them.

But in some cases, varicocele can cause pain that:

  • feels generally dull and aching
  • gradually gets worse throughout the day
  • sharpens after exercise or extended physical activity
  • feels less acute when you lie down

If you feel any pain and discomfort, see your doctor. They can assess your symptoms and advise you on any next steps. Enlarged veins can usually be treated with surgery.

If left untreated, varicocele can affect blood flow out of your penis. This can go on to interfere with sperm production and cause:

  • shrinking of an affected testicle, or testicular atrophy
  • loss of sperm production and motility
  • infertility

Blood clots

A blood clot (thrombosis) can develop in your veins when a mass of blood cells bunch together within a blood vessel. This limits or blocks blood flow through the vessel.

Penile blood clots usually develop in the penile dorsal vein, which is located on the top of your shaft. This condition is known as penile Mondor’s disease.

Blood clots can cause pain along with visibly enlarged penis veins. You may notice the pain more when you get an erection. The affected veins may feel firm or tender to the touch even when your penis is flaccid.

Penile blood clots can have many causes, such as penis injury, frequent or lack of sexual activity, or penile tumors. See your doctor right away if you notice any pain during an erection or when you touch the veins in your penis.

Certain surgeries

Surgeries performed on blood vessels in your penis, scrotum, genital area, or even your legs can affect blood flow to and from the penis.

Some surgeries that can cause a veiny penis include:

  • varicocelectomy, done to remove varicocele
  • vasculitis, done to reduce inflammation in a blood vessel
  • vein removal

See your doctor if you notice that your penis has become more veiny than usual following a surgery. Blood clots or improper blood flow can cause dangerous complications, so it’s crucial to get treatment right away.

Most of the time, there’s no need to worry if your penis veins look more pronounced than usual.

But if the appearance of your veins if causing you distress, talk with your doctor. They can assess your symptoms and diagnose any underlying issues.

You should see your doctor right away if you’re also experiencing:

  • pain during an erection
  • pain during ejaculation
  • swelling of your penis or one or both testicles
  • veins that feel hard or tender when touched
  • lumps on your penis or scrotum