Question: why are my veins blue

Simone Girdham answered on 10 Mar 2024:

It is the fluid inside your veins that makes them look blue.

Blood contains red blood cells (ie when you cut yourself the red stuff) which are made up of a thing called haemoglobin.
Haemoglobin is a very special compound. It loves oxygen and carbon dioxide.

As your blood goes through your lungs, you breathe in oxygen and this attaches to the haemoglobin. This turns the blood bright red.

Then, your heart pumps the haemoglobin around your body, via arteries, giving oxygen to your cells which helps you stay alive and grow.

Your body’s cells give back carbon dioxide to the haemoglobin, making your blood look a dark red.

The blood returns through veins to your lungs, where you breathe out the carbon dioxide.

Veins have thinner walls (think of a straw versus a water pipe) and some lie close to your skin, so you can see the blood through the wall.

Natural light now comes into play – think of a rainbow – light consists of different colours which are able to go different distances. Red light is absorbed by your blood, but blue light is unable to penetrate your skin, so the blood in your veins looks blue.