Facts About the Most Uncommon Blood Types You Probably Didn't Know

The Most Uncommon Blood Type
Blood groups are not evenly distributed; certain blood groups occur commonly, while some are exceedingly rare. Here, we will give you more information on rare blood types.
AB- and B- are the rarest blood types in the world. The Bombay blood group (hh), a relatively unknown blood type, is also one of the most uncommon blood types in the world. We know that A, B, AB and O are the four blood groups that can be Rh positive or negative (viz: A+, A-, B+, B-, AB+, AB-, O+ and O-). Among them, O+ is the most common; while AB- is the rarest blood type. The detailed explanation provided here will help in better understanding of the subject.
What are the Rare Blood Types?
AB- (AB negative)
This is the most uncommon or the rarest blood type in the world. It is found in less than 1% of the world's population. To be precise, people having this blood group comprise 0.45% of the world population, i.e., 1 in 175-200 people. AB- is also the rarest blood type in the US. People having this blood type can receive blood from all other RH negative blood types like O-, A-, B- and AB-.
B- (B negative)
The second most uncommon blood type is B- (B negative). It is found in 1.5-2% of the total world population, i.e., two in 70-100 people. People with this blood type can receive blood only from B- and O-.
A-, O- and AB+
- A-, O- and AB+ are also some of the rare blood types comprising approximately 3%, 4% and 5% of the total population. Blood types are not evenly distributed throughout the world. However, the ratio or the percentage to the total population, remains similar.
Bombay Blood Group (hh)
One of the most uncommon blood groups in the world, it is named so because its first case was discovered in Bombay (now Mumbai). In other parts of the world, it is found in 1 case among 250,000. But, in India (mostly East India), it is not so uncommon, found in 1 among 7000-8000 people. The H antigen is not expressed in this blood type.
Blood Types Explained
Blood groups (or types) and the Rhesus Factor (Rh factor) were discovered in 1901 by an Austrian scientist, Karl Landsteiner.
ABO blood group
Antigens and the Rh factor
According to Dr. Landsteiner, blood contains proteins known as antigens. Depending on their presence, blood is classified in different types as A, B, AB, and O. Now, we know that blood group is also referred to as positive or negative. This is known as the Rh (Rhesus) factor. It is also one of the important factors for determining the exact blood group of the person. Presence of the Rhesus factor D in the blood determines whether the blood group of the person is positive or negative. Therefore, in case antigen B and Rhesus factor (Rh D) are found in a person's blood, he has the blood type B+. Whereas, in absence of Rhesus factor (Rh D) for this antigen, it is B-.
Compatibility of blood groups Universal donor Universal recipient
O- Blood Group
Blood type O- is the universal donor, as it can be transfused into people of any other blood group. On the other hand, AB+ is the universal recipient, as people with this blood type can accept blood from any other type. However, today, the exact blood type is matched and only then transfused, in order to avoid reactions.

Today, there are several blood banks and organizations where it is possible to find a donor for rare blood groups. Although it is easy to identify the blood type of a person with the help of lab tests, it will really be helpful and save a lot of time in case the person knows his blood group. In case you do not know it, you can always get it checked in a laboratory.
Discovery and identification of blood types has been one of the most significant discoveries of this century as it has helped in prevention and treatment of various life-threatening conditions.