What is the rarest blood type? Here is the least common of the eight blood types

Blood — everyone's got it. In fact, an adult who weighs between 150 and 180 pounds has around 1.2 to 1.5 gallons of blood in their body. This makes up approximately 10% of an adult’s weight.

Someone's blood type is determined by "the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body," according to American Red Cross.

There are eight common blood types: A positive, A negative, B positive, B negative, O positive, O negative, AB positive and AB negative. But which is the rarest? Here's what to know.

What is the rarest blood type?

Based on statistics, the rarest blood type is AB negative. According to the American Red Cross, AB negative blood type occurs in "1% of Caucasian, 0.3% of African American, 0.1% of Asian and 0.2% of Latino American" populations.

There are over 600 other known antigens, and the absence or presence of them creates "rare blood types." Someone's blood type is considered rare if they lack "antigens that 99% of the people are positive for." If you lack an antigen 99.9% of people have, your blood type is "extremely rare."

The blood type of B negative is also uncommon, occurring in "2% of Caucasian, 1% of African American, 0.4% of Asian and 1% of Latino American" populations, according to the American Red Cross.

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What is the most common blood type?

The most common blood type is O positive, which is the blood type of 37% of the U.S. population.

To break down further, O positive occurs in "37% of Caucasian, 47% of African American, 39% of Asian and 53% of Latino American," populations, according to the American Red Cross. This blood type is in high demand since it is "the most frequently occurring blood type."

The second most common blood type is A positive which occurs in "33% of Caucasian, 24% of African American, 27% of Asian and 29% of Latino American" populations.

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What blood type is the universal donor?

The universal donor is O negative. Those with this blood type are considered universal donors since O negative can be used in emergency situations for transfusions on any blood type.

However, O negative is not an extremely common blood type. In fact, only 7% of the U.S. population has O negative blood. This blood type is found in "8% of Caucasian, 4% of African American, 1% of Asian and 4% of Latino American" populations.

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This article originally appeared on USA TODAY: What is the rarest blood type? Learn the eight types, compatibility