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Facts About Blood Types


Blood groups (A, B, AB, and O) are inherited. The presence or absence of an Rh factor on the red blood cells is what makes your blood type positive or negative. Blood groups (A, B and O) and Rh types are descriptions of certain antigens found on red cells. People with type A blood have A antigens on their red blood cells and lack B antigens; people with type B blood have B antigens and lack A antigens; people with type AB blood have both antigens, and people with type O blood lack both A and B antigens.

In addition, blood is typed as either Rh-positive or Rh-negative, referring to the presence or absence of the Rh antigen, which is named for the fact that it was first discovered in the Rhesus monkey. Most people (about 85 percent) are Rh-positive, and that figure is even higher for African-Americans and Asians.
Out of 100 people, about:
38 will be O positive
7 will be O negative
34 will be A positive
6 will be A negative
8 will be B positive
2 will be B negative
4 will be AB positive
1 will be AB negative

Who Can Receive Whose Red Blood Cells:

O negative can use O negative only

O positive can use O positive or O negative

A negative can use A negative or O negative

A positive can use A positive, A negative, O positive or O negative

B negative can use B negative or O negative

B positive can use B positive, B negative, O positive or O negative

AB negative can use AB negative, A negative, B negative or O negative

AB positive can use All Blood Types

Notice that all blood types can receive O negative red blood cells. This is why O negative is used in emergencies when there is no time to determine the blood type of the patient. This is also why donors who are O negative are always in high demand.

Blood is composed of cells suspended in a liquid. These cells -- red cells, white cells and platelets -- account for 50% of the volume of blood. The remaining liquid portion is plasma.

Red cells are as important to life as breathing in and out. They transport oxygen throughout the body cells. The oxygen provides the fuel, or energy, for all the work your body does. Red cells need foods rich in iron, such as meat, liver, eggs, green leafy vegetables and whole-grain bread to make them healthy. Red cells are produced in the bone marrow at a normal rate of about 17 million cells per second.

White cells, also known as leukocytes, are the protective cells in the blood stream. They attack bacteria by squeezing through capillary walls to reach the area of infection where they destroy bacteria. White blood cells are also made in the bone marrow and are produced at twice the rate of red blood cells.

Platelets are colorless cells or fragments produced in the bone marrow. They control bleeding by helping to form a blood clot. Platelets also assure that blood vessels stay "leakproof" in daily life by acting like an internal band-aid.
Plasma contains minerals, proteins, sugars and hormones and is the liquid through which all blood cells "swim".


Over 100 years ago, it was discovered that different people have different types of blood. The major types are 'O', 'A', 'B' and 'AB'.

For a blood donation to be helpful to a patient, there has to be a good match between the blood type of the donor and that of the patient receiving the blood. While receiving blood from someone of exactly the same type is fine, some types can happily mix with certain others, while others do not mix well. The common Type O can be given safely to patients with A, B or AB blood. But Type O patients can only receive blood from other Type O people.

Each major blood group is divided into Rh negative or positive types. On average, 45% of the population is Type O, 40% Type A, 10% Type B and 5% Type AB.



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