From A to O, your type matters

What’s your type? Are you a universal? A Rh negative or positive?

There is no judgment when it comes to giving blood.

“Many people don’t know their blood type, but when it comes to blood donations, all types are welcome,” said Lok Tse, supervisor of the transfusion medicine services and blood donor program for Cape Cod Healthcare.

There are eight distinct blood types: A+, A-, B+, B-, AB+, AB-, O+, and O-. Some are more common than others. Like the color of your hair and eyes, your blood type is a result of the genes you receive from your parents.

“Your blood type is determined by the presence or absence of the A and B antigens on the surface of your red blood cells,” said Tse.

Antigens are a type of glycoprotein (protein with carbohydrates attached). Blood group A has A antigens, blood group B has B antigens. Blood group O has no antigens, and blood group AB has both A and B antigens.

Your Rh status is determined by the presence or absence of the Rh antigen on the surface of red blood cells, which can be either positive or negative. Being Rh-positive or Rh-negative means that either you have the Rhesus D antigen on your red blood cells (positive) or you don’t (negative).

“Over 37 percent of the populations is O+, while less than 1 percent is AB-,”said Tse.

You don’t need to know your blood type to get through day-to-day life or even to donate blood, but it’s essential that lab tests determine your blood type before you receive a transfusion or before your donated blood is given to a patient.

“O negative is considered the universal donor, meaning that anyone can receive type O negative blood products,” he said. “O negative is always in high demand, because it’s compatible with all the blood types.”

That’s why type O blood is used in a medical emergency if the patient’s blood type is not immediately known.

A group O patient can only receive group O blood. A group A patient can receive group A blood or group O blood, and group B patients can receive group B blood or group O blood.

Matching Types is Essential

If transfused with A+ blood, an O+ patient would have a hemolytic transfusion reaction which can be life threatening. Other complications may include kidney failure, anemia and lung problems.

“We often need O positive and A positive blood, because they're the two most common blood types,” said Jonathan DeCoste, senior blood donor recruiter at Cape Cod Healthcare. “The majority of the population has those two specific blood types. In an emergency or if there's an accident, those are the most common ones that come up.

“Whether you know your blood type or not, we would still encourage you to come on out and donate blood. If you don't know your blood type, we’ll mail you a donor card with that information.”

Blood donors must be 17 or older (or 16 with parental permission) and there is no upper age limit. Donors must weigh at least 110 pounds and be in overall good health. Learn more about blood donor eligibility here.

The percentage of the U.S. population with each blood type:

Learn more about upcoming blood drives or read the story of a first-time blood donor.