How do blood types work?

Tina Smith June 04, 2019

How do blood types work?

They are inherited. Like eye color, blood type is passed genetically from your parents. Not all blood is alike. There are eight common blood types and many rare ones.

Your blood type is determined by your ABO type and a negative or positive Rh factor. But you may be wondering why you have the blood type that you have and what it means to your health.

Most people are familiar with ABO blood types and the Rh factors.

Those are determined by genes inherited from your biological parents. You inherit a gene from each parent so your blood type may not be the same as your parents.

For example:

  • If you inherit an A from one parent and an O or A gene from another parent, you will have type A blood.
  • Type B from one parent and type O or another type B gene from the other parent will give you type B blood.
  • But inherit an A gene from one parent and a B from the other and you have AB type blood.
  • Those with type O blood have inherited the O gene from each parent.

blood type chart

The Rh factor works in a similar manner. Rh is a (protein) that you either have, making you positive, or don’t have, making you Rh negative.  

  • If both your parents are Rh negative, you are probably Rh negative.
  • If either parent is Rh positive, you could be either Rh negative or Rh positive.

rh factor chart

How can I find out my blood type?

A simple blood test can determine your blood type. Your doctor can do this or your blood may be tested if you undergo a medical procedure.

But there is an easy way to learn your blood type – donate blood.

When you donate blood, your donation will be tested and typed. Most blood centers let donors know their blood type, including OneBlood. All OneBlood blood centers include a mini-physical with information on your blood type, overall cholesterol level, blood pressure, pulse and temperature.

You don’t have to know your blood type in order to donate.

People may think that they need to know their blood type before they donate, but you can donate without knowing your type. Blood centers test all donated blood to determine the type and to make sure patients receive the correct blood type.

Blood type is important because during a transfusion, the body will reject any blood that is an incompatible type. But the blood type doesn’t need to be an exact match in all cases.

O negative blood is known as the universal donor blood type because it can be given to anyone in need of a transfusion. For this reason, hospitals rely on it in many emergency situations.

However those with O negative blood must receive O negative blood if they need a transfusion. So it is doubly important for people with O negative blood to donate. 

Even if you don’t have O negative blood type, you should consider donating blood. Patients in hospitals need blood and products like platelets, which are a part of your blood, for many different reasons. Doctors work to match the blood type as closely as possible to give the patient the best chance of recovery.

You can learn more about blood types and how you can Target Your Type when you donate blood.

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Tina Smith

With a career in communications spanning two decades, Tina Smith is OneBlood’s content manager, taking care of the company’s website and intranet. She also help write the postcards and emails that donors may find in the mailboxes. Helping save lives through her work brings a sense of satisfaction that few jobs can offer.

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