Why are Veins Blue?

Why are veins blue when our blood is red? This is a question that may have come up at some point in your life, possibly in childhood, since we’ve known from a young age that our blood is indeed red. To find the answer, we need to look to science.

Your veins appear blue due to the effect of blue light being more effective at penetrating your skin to make the veins visible. Blue light has a shorter wavelength than other colors besides violet, so it can reflect back to your eyes faster.

We will go over in more depth why your veins appear to be blue despite having red blood flowing through them.

The Science of Why Veins Appear to be Blue

When you look at the inside of your wrist, top of your hand, or even on your legs, any visible veins may appear to be blue or sometimes even more of a green or purple shade. How is that possible when the blood inside the veins is red? Some of our childhood theories may suggest that our blood doesn’t turn red until it is exposed to the air. However, blood is always red regardless of when and where it is. It all comes down to science.

The reason your veins appear to be blue is due to the light penetrating through your skin as well as layers of fat. The light hitting your skin is white which consists of all of the colors in the spectrum. You have both blue and red light penetrating the skin, but blue light is more effective than red for this purpose.

Red light has the longest wavelength in the spectrum at 700 nanometers and so it has the furthest to travel before returning to your eyes. The red light can easily travel through the skin, but it gets absorbed by the hemoglobin rather than directly reflecting the color back to your eyes. If you were to view your arm under a red light, you would notice that your veins appear dark and easily visible. Sometimes, this technique is used by phlebotomists to locate your veins when drawing blood, although they may use an infrared light due to its longer wavelength.

Blue light has the shortest wavelength, besides violet, at 450 nanometers. Since it has a shorter distance to travel, it can make the trip back to your eyes faster. It scatters more easily than red light, so it does not readily penetrate through your skin. Instead, it is mainly deflected back to the eyes. When blue light hits your skin, it deflects back to your eyes and makes you see what appear to be blue veins. If you were to view your arm under a blue light, you may not be able to locate your veins at all. Your entire arm would appear blue as the light is reflected back.

Is Your Blood Always Red?

The whole time your blood is pumping through your veins or bleeding from a cut, it is red. The combination of hemoglobin and oxygen make your blood red. As a young person, you may have believed that blood was blue until it reacted with oxygen in the air when you are bleeding. However, your blood is always red regardless of exposure to air, since it receives oxygen within your body. For example, when you donate blood or have it drawn, it is deoxygenated but you can clearly see in the pouch or vial that your blood is red.

The shades of red your blood appears may vary at times though. Your heart begins by pumping out blood to the lungs which is then a bright red color. When your blood is on its journey back to the heart, it is less oxygen rich than when it was first pumped out by your heart. Blood with a lower oxygen content will be a darker red hue and this can appear blue through your veins.

What Color are Your Veins?

The veins themselves do not have much of a color. Instead, they take on the color of your blood just as a clear straw would take on the color of your beverage as you sip on it. Blood that is newly pumped from the heart will display the brightest shade of red, while deoxygenated blood will show a darker red color. This deoxygenated blood will be the most likely to appear as blue through your veins.

Why Might Veins Look Different on Different People?

While veins mainly appear to be blue, the visibility of the veins and the particular shade vary based on several factors.

Vein visibility and color may vary based on:

• Location of the vein – Veins that are closer to the surface of your skin are less likely to appear blue.
• Thickness of the vein – Narrow veins may not appear blue.
• Skin color – People with very light complexions are more likely to have visible veins. Those with warm undertones to their skin may have veins that appear more of a green or blue-green shade.
• Age – Veins become more visible as you age since your skin becomes thinner and your veins weaken and stretch out, allowing blood to pool in the veins.
• BMI – People who have a higher body mass index may have more visible veins due to excess pressure on the veins.
• Genetics – Some people simply have visible veins in their family history.

Summary

Now you know why your veins appear to be blue. It is all because of the science of light and how it reflects colors back to our eyes. Regardless of which color your veins appear, it is important to practice healthy vein habits to protect your health. Awareness of the symptoms of vein disease and what makes you more susceptible to it can help you make the changes you need to promote the health of your veins. As much as home treatments can help alleviate the symptoms of vein disease, they are not likely to eliminate vein problems. Leaving vein disease untreated can lead to future complications, so it’s important to address it.

While a healthy diet and lifestyle are extremely helpful for decreasing the appearance of varicose and spider veins, it is important to seek out professional care if the problem persists. If you are experiencing symptoms from vein disease that do not respond to diet and lifestyle changes, contact us today to book an appointment.