Have you ever donated blood? If so, you probably remember them asking you for your blood type. But you might not know that even if you tell them your type with confidence, they still test your blood to confirm this information. So, what’s the big deal about blood types? What does it mean and why is it so important?

What is blood type?

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Let’s take a step back to your high school biology class. You remember that our blood is composed primarily of red blood cells and plasma. Of course, there are other items like platelets and white blood cells, but that’s a topic for a different article. For some red blood cells, there can be what’s called antigens which act as identifiers. Not everyone has these antigens on their blood cells. And based on their presence on the cell’s surface — or lack thereof — and antibodies within the plasma, medical professionals can determine your blood type. In total, there are four main blood types: A, B, AB, and O. Depending on your blood type, there may be antibodies present in your plasma that will be the opposite of your type. However, there are exceptions.

● Type A will present A antigens on cell surfaces with B antibodies in plasma

● Type B will present B antigens on cell surfaces with A antibodies in plasma

● Type AB will present A and B antigens on cell surfaces with no antibodies in plasma

● Type O will present no antigens on cell surface with A and B antibodies in plasma

How is your blood type determined?

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Blood types can be identified with a simple screening test for the antigens mentioned above. But genetics is the real factor behind your blood type. You get your blood type from your parents, and the genes can be dominant or recessive. Your blood type is determined by three distinctive genes. Types A and B are dominant while O is recessive. So, if one parent passes an A gene, but the other gives an O, you will be type A. However, if one parent passes an A, and the other a B, the co-dominant genes result in a type AB child. The possible combinations include:

● Type A: AA or AO

● Type B: BB or BO

● Type AB: AB

● Type O: OO

What about this positive and negative thing?

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Now we’ll go a step further and talk about the Rhesus or Rh factor. You’ve probably heard people say whether they’re positive or negative. This essentially means that in addition to their blood type, their red blood cells either contain or lack an additional antigen. So, there are four antigens that are screened when testing blood. The only two options with an Rh screen is to be Rh negative or positive. If you are positive, it means that your blood cells do contain this antigen. And of course, a negative result means your blood cells don’t have this antigen, but you do have Rh antibodies.

The importance of blood types

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Because of the potential for antibodies in your plasma, it’s crucial that blood is properly categorized. Giving someone the wrong blood type, or the right blood type but the wrong Rh factor, causes their body to reject the blood. An Rh-positive person can receive blood from both positive and negative donors while an Rh-negative person can only accept Rh-negative blood.

Pregnancy and Rh factors

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Any woman who’s ever been pregnant knows that one of the first tests your obstetrician will perform is to confirm not just your blood type, but your Rh factor. For Rh-positive women, there is no concern, and they can continue on as normal. For an Rh-negative mother, there is a risk of Rh incompatibility. If the fetus is Rh positive, the blood between mother and fetus could potentially mix, and the mother’s antibodies could attack the fetus and cause complications. While this usually isn’t an issue for first-time Rh negative mothers, it can be a real concern in later pregnancies. Because of this, pregnant women who are Rh-negative usually receive a Rhogam shot to avoid developing antibodies.

So how many blood types are there?

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If your head isn’t swirling yet, here are the possible combinations:

● A+/A-

● B+/B-

● AB+/AB-: AB+ can receive blood from anyone because they lack antibodies for blood type and Rh factor

● O+/O-: O- is the universal donor because they lack all antigens for blood types and Rh factor

Blood types and personalities

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In many parts of Asia, blood type is treated like your horoscope sign and is said to influence your personality. Just like with Western star signs, some blood types are viewed more favorably depending on the person’s gender. Type A is considered the most ideal for anyone while type B men are viewed unfavorably as playboys.

While knowing your blood type is not something that you might need on a daily basis, it’s always a good idea to have that information on hand in case of an emergency.

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