Blood donation

How to Know What Blood Type I Have

Max. D Gray
By Max. D Gray. Updated: July 10, 2024
How to Know What Blood Type I Have

Knowing a person's blood type is important for both giving and receiving blood. Although in emergency situations, most patients will be given O-negative blood as this works on all blood types. When we have non-emergency medical procedures which require blood transfusions, we will need to know our blood group. Since it is not something which needs to be discussed in routine medical consultations, many of us have either forgotten our blood type or never even knew it in the first place.

As with other characteristics such as eye color, our blood group will be determined by genetic inheritance. They all depend on the proteins exhibited by the red blood cells that circulate through arteries and veins. To discover how to know what type of blood you have, the different blood groups that exist and their respective compatibilities, keep reading oneHOWTO.

You may also be interested in: Can You Donate Blood if You Have Tattoos?
  1. What types of blood are there?
  2. What are compatible blood types?
  3. How do I know what blood type I have?

What types of blood are there?

There are two classifications to determine the blood group: the AB0 system and the RH factor. In the first classification, the letters in the acronym ABO correspond to three different blood proteins (A, B and O) which are either able to or not able to coat the red blood cells. The blood may also have antibodies that react to another type of blood that is not of its group.

The 4 blood groups of the AB0 system are the following:

  • A: contains A proteins and anti-B antibodies.
  • B: contains B proteins and anti-A antibodies.
  • AB: contains both proteins, but neither of the antibodies.
  • 0: contains no protein, but does contain both types of antibodies.

For the second classification model, blood can also be classified according to whether it has another group of proteins called Rhesus factor (RH factor) in the red blood cells:

  • RH +: if you have the cell surface proteins.
  • RH -: absence of cell surface proteins.

In this way, there are a total of 8 different blood groups :

  1. 0 positive (0+)
  2. 0 negative (0-)
  3. A positive (A+)
  4. A negative (A-)
  5. B positive (B+)
  6. B negative (B- )
  7. AB positive (AB+)
  8. AB negative (AB-)

In the USA, approximately 38% of the population belongs to blood group O positive (0+), with the next largest group being A positive (A+) at 34%. This is reflected in the rest of the world as a whole since O+ is the most common blood type. The rarest blood type in the world is AB negative (AB-).

However, individual countries and ethnicities do differ in terms of blood type distribution. For example, B-type blood is the most common blood group in the Middle East, but it is the lowest group in Southeast Asia.

How to Know What Blood Type I Have - What types of blood are there?

What are compatible blood types?

Taking into account the eight blood groups that exist, these are their compatibilities between them:

  • A+: is one of the most common blood groups. You can donate to group A positive and group AB positive. In addition, a person with this blood type can receive blood from A positive and A negative and from 0 positive and O negative donors.
  • A-: individuals belonging to this group can donate blood to AB positive and AB negative persons and to A negative and A positive. They can receive blood from A negative and 0 negative donors.
  • B+: you can donate to AB positive and B positive people, and you can receive blood from 0 positive and O negative and B positive and B negative donors.
  • B-: this blood group can donate to AB positive and AB negative and to B positive and B negative. They can receive donations from 0 negative and B negative donors.
  • AB+: donates blood to AB positive and is a universal recipient, i.e. people with this blood type can receive blood from all other blood groups.
  • AB-: donates blood to AB positive and AB negative and receives blood from A negative, B negative, AB negative and 0 negative.
  • 0+: donates to A positive, B positive, AB positive and 0 positive and receives blood only from 0 positive and O negative.
  • 0 -: it is a blood group that can donate to all the other types, it is the universal donor, but it only receives blood from O negative donors.

How do I know what blood type I have?

In order to identify your own blood group, you need to take a simple blood test. Despite the relative ease with which you can determine your blood type, you will need to have a reason to ask medical professionals to test your blood. This may affect your insurance, but you can also ask for it during your next checkup.

For those who cannot spend the money for a private blood test, you can always donate blood. Not only is this an important civic duty, but you can find out your blood type when you sign up as a donor with certain services. For example, the Red Cross will give you a blood donor card. They are legally required to test your blood and they will also notify you if you have any conditions which prevent your blood from being valid for donation.

Take a look at the different criteria which will determine whether you can donate blood.

To determine your blood type accurately, the AB0 test must first be done to find out the blood group. The blood sample is mixed with antibodies A and B to check their reaction. The second step in determining blood type involves mixing the blood sample with some serum for the RH factor test.

Finally, if you want to know how to know what blood type I have at home, you can check your medical files. If you still have contact with home, you may have files from tests carried out when you were a child. Many of these documents will have your blood type listed. For some, knowing your blood type can be as simple as asking a parent as they may be likely to remember.

If you are thinking of donating blood, our article on whether you can donate blood if you have tattoos might provide some specific help.

This article is merely informative, oneHOWTO does not have the authority to prescribe any medical treatments or create a diagnosis. We invite you to visit your doctor if you have any type of condition or pain.

If you want to read similar articles to How to Know What Blood Type I Have, we recommend you visit our Diseases & secondary effects category.

  • Statista. (2021). Average distribution of blood types in the United States as of 2021. Retrieved from:
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