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Things Your Blood Donation Center May Not Be Telling You

I'm currently a senior studying public health at a state university. I also worked as a clinical specimen processor for almost 5 years.


Antigens: a blood protein that provoke the immune system to produce antibodies. These cells are found on the surface of red blood cells. It is this type of protein to which that antibodies respond. Think of antigens as the people that do belong in a region (native antigens) or those that are "wanted criminals" (foreign antigens).

Electrolytes: medical term for what are known as "body salts" found in blood plasma. Electrolytes are necessary to maintain cellular electrical environment, so that cellular communication can occur via electrical impulses (especially in muscular, cardiac, and nerve tissue). These are the body salts found within sports drinks, such as Gatorade (commonly sodium chloride or potassium chloride).

Epitopes: the portion of antigens that antibodies do or don't respond to, depending on whether the antibody recognizes the antigen as native (typically friendly) or as a foreigner (potentially hostile). Think of epitopes as being the face of people. It is the head shots taken of people that are used as a reference by law enforcers to determine whether someone is a regular civilian or a wanted criminal.

Erythrocytes "red blood cells (RBCs)": flexible, biconcave disc-shaped cells mainly responsible for carrying oxygen to cells and carbon dioxide out of cells. Think of red blood cells as being the vehicles which house antigens and hemoglobin.

Hemoglobin: a protein containing iron responsible for the transportation of oxygen found on the surface of RBCs. This protein is responsible for blood's red color in many species (including humans), due to the oxidation of the iron found within hemoglobin. You can think of hemoglobin as being similar to a car's paint color, with the car representing the red blood cell.

Immunoglobins "antibodies": a type of immunoglobin of blood produced by the immune system in response to the presence of antigens. Think of the antibodies as the policemen performing roadside searches in every passing car for wanted criminals (foreign antigens).

Leukocytes "white blood cells "WBCs"): a group of blood cells that are white in color. The main function of white blood cells is to fight off invading antigens after being "informed" by antibodies of their presence. The process of fighting off an infection by one's "immune system" refers to the various types of leukocytes working together to fight off disease.

Plasma: straw-colored liquid in which red blood cells, white blood cells and platelets are suspended. Plasma contains many substances, such as water, electrolytes, antibodies, hormones, chemicals, glucose, and proteins (ex. albumins, globulins, and fibrinogens).

Serum: blood plasma minus the coagulation (blood clotting) factors.

Thrombocytes "platelets": lens-shaped cell fragments that are involved in the process of coagulation "clotting". Their main function is to aide in the formation of blood clots to minimize blood loss.

Whole Blood: blood drawn from donor with none of its components removed.

Blood Components By Percentage

There are various types of blood donations

Often times when someone hears about blood donations, they may image a phlebotomist drawing blood from a patient with a pint of blood in a beside the patient, and the patient then walking away within 30 minutes to an hour after recovering (the process of drawing blood taking about 5-10 minutes). What you may not know is that you can actually donate specific components of blood. After blood is drawn from the patient, it is sorted into 3 main components (erythrocytes "red blood cells (RBCs)", plasma, thrombocytes "platelets" and leukocytes "white blood cells (WBCs) in a process called aphresis or automated blood collection "ABC"). Sometimes, the separation or drawing of specific blood components is done onsite. It is because blood is divided into these 3 components that your blood donation center will say "1 unit of blood can save up to 3 lives". The process of donating blood to yourself is known as autologous blood donation (done only when prescribed by a healthcare provider).

Whole blood donation: this is the most common form of blood donation many picture when they hear about someone donating blood. When people donate whole blood, they are donating all of their components on-site and is separated in a blood bank lab. Individuals can give whole blood close to every 8 weeks (about 56 days).

Red blood cell donation "double red cell donation": a lot of people have previously chosen to specifically donate red blood cells. Instead of donating 1 unit of blood with all its components, this kind of blood donation involves donating 2 units of red blood cells. After the blood is drawn and the RBCs are separated onsite from the other blood components, the other components are then "put back" into the donor's body. Patients with chronic anemia, trauma, or internal injuries benefit most from RBC donations. Individuals with type O blood are highly encouraged to donate RBCs.
Due to the nature of this kind of blood donation, additional requirements must be met in order for an individual to be qualified for this type of donation. This type of blood donation takes an additional 30 minutes to perform in comparison to whole blood donation. An individual can donate double RBCs about every 16 weeks.

Platelet donation: when an individual participates in platelet donation, some plasma is also collected while platelets are gathered. Depending on a donor's gender, weight, height, hemoglobin levels, and platelet count that day, the phlebotomist may take anywhere between 1-3 units of platelets. People undergoing chemotherapy or are recovering from a bone marrow or organ transplant benefit most from platelet donations. Individuals with AB type blood are encouraged most to donate platelets, although those with type A and B blood are also great platelet donor candidates.
This type of blood donation takes approximately 1.5-2 hours (there will be a television screen in front of the donor for entertainment purposes). An individual can donate platelets generally every 3 days, although platelet donors typically donate every 2 weeks (up to 13 times a year).

Plasma donation: plasma is a highly sought after component of blood, as many of blood's healing components are found within plasma. This can involve either donating plasma only or mostly plasma and some platelets simultaneously. If you donate plasma, it will not be used unless you donate multiple times within a 6 month period (first time is used to be tested for safety to see if it can be used for donating). People with type AB blood (especially AB+) are sought after for plasma donations, as their plasma is considered to be "liquid gold" (can be given to any blood type). Patients with cancer, severe burns, hemophilia, and various life-threatening diseases highly benefit from receiving plasma donations.
For first time donors, the process takes about 2-3 hours and about 90 minutes for multiple time donors. An individual can donate plasma every 3 days or twice a week, up to 24 times a year.

Diagram demonstrating the antigen-antibody relationship

Diagram demonstrating the antigen-antibody relationship

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Your ABO blood type may not test the same every time

You may have heard that blood type never changes throughout our lifetime. There are also many stories you may have heard about someone testing as one blood type one day and testing as something completely different within a few years of re-testing (or even within a few days!). Nurses, physicians, and other healthcare providers may end up being baffled by this mysterious "change" in blood type. What they may not realize is that there are in fact many subgroups within the ABO and Rhesus D factor blood systems alone. Individuals with these blood subgroup types will not test the same as others using the standard blood typing tests. Further testing must be done in order to correctly "type" the blood of these individuals. It is extremely important for individuals who's blood type test results vary on the standard blood test to have their blood further analyzed.

ABO subgroups
One of the more surprising facts about the ABO system is that there are actually subtypes of the ABO antigen system. There are 2 main type A blood subtypes (overall about 20), which are A1 (about 80% of type A people) and A2 (about 19% of type A people). Although very rarely observed, type B blood has approximately 5 subgroup types. Due to the variations of the A and B alleles, there are a few variations of AB type blood with the main ones being A1B (most common AB type) and A2B. Individuals with type O blood may have one of a few type O subgroups, usually one of the 3 main O types (O01, O02, or O03). Perhaps one of the more intriguing subtypes are among the cisAB group, which is inherited by 1 parent (mother or father).

Generally, those who have one of the ABO blood subgroup types will have less of their associated antigens and may even have some of the associated antibodies (ex. A2 individuals may have some A antibodies present in the plasma). However, the antibodies are often fewer in number and generally are mostly inactive at body temperature (thus often times aren't of serious clinical significance). Sometimes, the A and B antigens may have additional antigens attached to their surface and therefore have different molecular shape than other forms of these antigens. As far as the type O subgroups go, it's currently debated as to whether the genetic differences between the subgroups results in different proteins.

Rhesus Factor
There are actually over 50 forms of the Rhesus factor protein, although 5 main groups are of the most clinical significance (D, C, c, E, e). In the standard blood typing system, the "Rh positive" or "Rh negative" status refers to the presence or absence of the Rhesus D protein. Incompatibility reactions between Rh D positive and Rh D negative blood types are currently the most violent blood type incompatibility reactions known. The most common example of this incompatibility causing problems is between a mother with Rh negative blood and a fetus with Rh positive blood, should the fetus not be the mother's first child. Should the Rh D positive blood be mixed with the Rh D negative blood, antibodies to the Rh D proteins will be made by the mother's immune system and thus "attack" the fetus' blood. This may lead to the fetus developing hemolytic disease, which results in problems such as anemia (due to the destruction of RBCs), jaundice (yellowing of the skin), and dyspnea (difficulty breathing).

Like the main antigens in the ABO blood group system, the Rhesus D factor also has different variations in how it is expressed. Because of these variations, blood test results may vary and may be a source of confusion for healthcare providers and their patients alike. Individuals who have these variations of the Rh D allele may test as being Rh D positive one test and Rh D negative on the next. There are 2 main variations in which the Rh D antigen expresses itself.

Partial D: this expression of the Rh D antigen is thought to be a hybrid protein, mixed between the RhD and the RhCE proteins. The Rh D antigen for those who have the partial D variant of this antigen are missing some of the epitopes (the portion of antigens that antibodies do or don't respond to) of the Rh D antigen. They are similar enough to the normal Rh D protein to attach itself to the surface of RBCs but do not have all of the epitopes. Due to the reduced number of epitopes on the surface of these Rh D antigens, Rh D antibodies may form should normal Rh D antigens be introduced. Because of this theoretical reaction, individuals with this variation of the Rhesus D factor should not receive blood from Rh positive individuals.

Weak D: when an individual has weak D, this means they have fewer Rh D antigens found on the surface of their RBCs. This is usually caused by a swapping of an amino acid swap occurring on the surface of the Rhesus D antigens. Since there are no changes to the epitopes of the Rh D antigens, it is typically safe for individuals with weak D type blood to receive Rh positive blood. As always, precaution should be taken in the process of blood transfusions and blood donation.

In conclusion, it is these subgroups within the ABO and Rh D blood group systems alone that may be why some people's blood type test results will "differ" or "change" each time their blood is tested. These differences could also account for some blood type incompatibilities, even if the standard blood tests show the donor and recipient have matching ABO and Rh D blood types. There is of course the possibility the individual previously had a bone marrow transplant (where RBCs are created) or their blood type was mislabeled in the lab, although these are entirely different subjects in themselves. Unfortunately, not all healthcare providers are knowledgeable about blood type enough to recognize there are in fact differences among the ABO blood groups. Of course, this isn't their fault, as these subtypes are recognized only by accident (and further testing shows the individual has a rare blood type).

This diagram visually summarizes the differences in presentation of the RH D variations.

This diagram visually summarizes the differences in presentation of the RH D variations.

This chart demonstrates the standard ABO blood typing test results and each result's associated ABO and Rh D blood type.

This chart demonstrates the standard ABO blood typing test results and each result's associated ABO and Rh D blood type.

This diagram demonstrates the various ABO blood types and the antigens present on the surface of the red blood cells for each ABO blood type.

This diagram demonstrates the various ABO blood types and the antigens present on the surface of the red blood cells for each ABO blood type.

O- is not (quite) the universal blood donor

You may have heard of O negative "O-" blood being referred to as the universal blood type. What does this mean exactly? What blood bank specialists mean by O- blood being the universal blood type, what they mean is that this blood type is the universal red blood cell donor. After whole blood is drawn from the body, it is separated into 3 main individual components (plasma, white blood cells "WBCs" and platelets, and red blood cells "RBCs") either on-site with special equipment or in a lab. Because there are no A or B type antigens on the surface of O- red blood cells, O- blood is sometimes referred to as the universal RBC donor. However, type O- blood has AB and Rhesus D factor antibodies in its plasma.

O- type blood still has H antigens on the surface of its RBCs, which are the building blocks of the sugars required for the production of A and B type antigens. For those with O type blood, this antigen remains unmodified and therefore unable to produce either A or B type antigens. Some individuals lack this H antigen entirely; this extremely rare blood type is known as Bombay Blood, named so after the region in India where this blood type was first discovered in 1952. On the standard blood typing test, people with this blood type will be mistakenly typed as having type O- blood. Further testing has to be done in order to reveal whether or not someone has the Bombay phenotype. Individuals with Bombay Blood can only accept RBCs from another Bombay Blood group individual, as they have H antibodies present in their plasma (meaning no H antigens on the surface of their red blood cells).

In short, individuals with O- blood are highly encouraged to donate whole blood by say the American Red Cross mostly for their RBCs. All components of an individual's blood are able to be used, although when the various components can be used depend on the donor's blood type, the recipient's blood type, and what the recipient needs. Anyone who has the Bombay Blood phenotype is highly encouraged to donate their own blood in the case that they may need it for themselves in the future, as this blood type is very rare (thus is difficult to obtain)!

Blood Type Compatibility Chart

Blood TypeCompatible RBC RecipientsCompatible Plasma RecipientsCompatible Platelet Recipients


AB+, AB-


ABO RhD negative






AB+, AB-, A-, A+

A group, O group

A-, O-


AB+, A+

A group, O group

A+, A-, O+, O-


AB+, AB-, B-, B+

B group, O group

B-, O-


AB+, B+

B group, O group

B+, B-, O+, O-



O group



ABO RhD positive

O group

O+, O-

* Except Bombay Phenotype




There are actually hundreds of blood types

Usually when someone asks you what your blood type is, you may respond by saying "I don't know" or something such as "I studied really hard for the blood test and got an A+". In your high school anatomy class, you probably learned there are 8 blood types. What you probably won't hear is something like "I have Kidds in my blood" or "my blood's name is Junior". Since Karl Landsteiner discovered the ABO blood group in the early 1900s, many other blood groups have been discovered. In 2012, biologist Bryan Ballif from the University of Vermont identified the genetic sequence for the Langereis and Junior blood groups, which are associated with anticancer drug resistance. There are currently over 30 known blood groups (and thus hundreds of blood types) recognized by the International Blood Transfusion Society.

Testing for all the known blood group systems are done within blood bank labs. For now, the ABO and Rhesus D blood group systems are of the most clinical significance, although this may soon change with the recent discovery of the Langereis and Junior blood types. Hemolytic disease as a result of mother-fetus blood type incompatibility can result from any kind of blood type incompatibility. However, this disease is most commonly associated with Rhesus D factor incompatibility (this assumption has proven to be fatal in some cases). It's also due to simplicity sakes that only these blood groups are discussed by blood organizations, such as the American Red Cross. In the video below, the standard procedure for blood typing is demonstrated.

In conclusion...

There are many misconceptions regarding blood type and blood donation based on outdated information and general misunderstandings regarding blood. Much of this information does not go past the understanding of blood from information that is over 60 years old (or older). Many blood groups have been discovered since the Rhesus and ABO blood systems were identified. Before these other blood group systems were discovered, it was assumed that type O blood was the universal donor until the Rhesus factor was discovered. After the Rhesus factor was found, O- blood was thought to be the "universal donor" up until the discovery of Bombay blood and other blood groups. No one blood type is superior or more medically needed to others, despite what outdated ideas (and even conspiracy theories) may unintentionally portray.

Stay tuned for more hubs regarding blood from this vampire scientist in the making.

ABO Blood Type


Christina Garvis from United States on January 02, 2019:

I found this article rather intriguing; I didn't know before that there were subgroups in the ABO groups at all!

Sapphyre Opal (author) from United States on August 20, 2014:

Thanks VirginiaLynne :) I have a lot of interest in understanding life science topics, and had my interest peaked in learning about blood. It's interesting knowing that people can actually get paid for their time in donating their plasma. I myself am also considering that option (don't really see why not), although it's more of a matter of finding the time to do so.

Unfortunately, a lot of healthcare providers in the clinical setting have a rather poor understanding of blood typing and it is costing some people. There are a lot of mysteries they come across in the clinical environment that would be resolved if they were more educated about the science of blood and such, and not simply thinking "why would I need to know this to do my job?" Hopefully with the discovery of new blood groups that are related to cancer drug resistance, healthcare providers will think twice about their understanding of blood types.

In this, I also hope they start to eventually personalize their approach to healthcare and stop seeing simply numbers in their patients. Everyone has a unique biology afterall.

Virginia Kearney from United States on August 19, 2014:

Very interesting information! I used to do whole blood donation and have been considering plasma donation but hadn't gotten around to doing it. I didn't know about the different blood groups. Well written and thorough.

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