What happens when you donate blood?

Robert Rainer, MD

Pathology

Most of us have seen blood drives, where different organizations offer the chance to donate blood for a good cause. But for those who haven’t yet donated, there may be some questions they want answered before they decide to donate. Why is donating blood important? What happens when you donate blood? Is the process painful? How is donating blood different from donating plasma?

Pathologist Robert Rainer, MD, answered common questions about donating blood and why you should embrace this simple, life-saving opportunity.

Why is donating blood important?

“Blood donating is important because, quite frankly, there is no substitute,” said Dr. Rainer. “We cannot manufacture blood; it has to come from other people. We can store blood and have it available when and where we need it, but we can’t safely store blood forever. We always need to look ahead and replenish our supply.”

In addition, not all blood is usable for everyone. Different individuals have different ‘blood types,’ called A, B and O or combinations of A and B (think AB blood), as well as the blood type being known as ‘positive’ or ‘negative.’ Not all blood types can receive other blood types through donation, as the body will reject the unfamiliar blood. However, O negative donors are often called “the universal donor,” as their blood is universally accepted by all other blood types.

You can see more about how blood types interact in this informative Red Cross explanation.

Blood donation helps to ensure a variety of blood types are available in the event of traumatic injuries, diseases or other conditions. Having multiple blood types available can end up being the difference, for the patient, between life and death.

What happens when you donate blood? Does it hurt?

“The truth is, yes, it does hurt a little,” said Dr. Rainer. “I like to tell people giving blood is not fun. It takes time, and we do have to put a needle in your arm. While it can be rewarding, there is a bit of sacrifice on your part.”

The only real discomfort is with the initial placement of the needle, which only lasts a few seconds. Most people look away, and say it was not as bad as they imagined it would be. The process of placing the needle feels similarly to when you give blood at the doctor for standard blood tests.

The needle remains in place for about 15 minutes when someone gives red cells and about an hour to give platelets. 

“We realize you are giving a gift,” said Dr. Rainer. “We do everything we can to make this gift as painless as possible.”

How do you ensure blood donation is safe?

“There’s a lot that happens during the process leading up to donating blood,” said Dr. Rainer. “Our goal is to provide a safe, adequate and effective blood supply to our communities. To promote safety, we ask screening questions, which may feel very personal or potentially embarrassing, but we’re really just looking to identify potential risks. You’ll answer these questions privately, and it’s important to be truthful and honest.”

Questions asked during the screening process might include:

• Are you feeling well today?
• Have you ever had hepatitis?
• Have you been or could you be pregnant?
• What is your recent travel history? Have you traveled internationally within the past six months?
• Questions about potentially risky behaviors

“Once the initial screening is over, we’ll perform what we call a mini physical,” said Dr. Rainer. “We’ll check your vital signs, your hemoglobin level and make sure that you’re healthy enough to donate. We will not take any action that could make you anemic. Most people won’t have any problems donating once at this stage, but we still have these built-in guard rails to protect you.”

How much blood do you lose during blood donation?

“We take out roughly 500 milliliters of blood,” said Dr. Rainer, “And about 50 milliliters of blood in separate tubes that we use for further testing. All in all, this works out to be roughly a pint of fluid, or about 10% of the blood in your body.”

While most people tolerate this easily, some people might feel a little drained or fatigued for two hours or so afterward. That’s one reason blood donation centers usually have refreshments available, with drinks and snacks to help people replace the volume they lost.

Blood donors also have a limit on how often they can donate, to ensure that no one donates too much blood and becomes ill from anemia as a result. Whole blood donors will usually be told to wait 56 days between donations, while those who donate platelet or plasma need to wait 14 days between donations.

All donated blood is tested for a variety of potential bloodborne pathogens, both for the organism itself through DNA/RNA testing and by looking for the antibodies that would show the donor’s body was responding to disease-causing organisms. If a positive result is found, the donor is notified to ensure they are aware they may need to seek further medical treatment.

Thanks to current inspections by the FDA and other accrediting agencies, plus the ongoing testing of donated blood for pathogens, transmission of infection through blood transfusions is currently very, very rare.

How is donated blood processed?

“There’s a lot of processing to ensure usefulness and the best possible long-term storage,” said Dr. Rainer. “We spin the bags in a centrifuge, separating the plasma (or liquid part) from the red cells. We flash freeze the plasma within 24 hours in order to store this product for one year. Red blood cells are kept in a refrigerator to prevent bacterial growth, and the red blood cells are stored for up to 40 days.”

Different blood types are used at different rates, so group O blood will likely be used up within one week after donation, while group A blood might take 30 days before being used.

When it comes to platelets, Dr. Rainer noted, a different process is used to remove platelets from the blood and return the plasma and red blood cells to the donor. The collected platelets are cultured for potential bacteria and rest for two days to ensure they aren’t contaminated.

Once processed, the collected platelets have a shelf life of about five days, as they are not refrigerated.

All donated blood products are shipped to hospitals using very strict controls for safety and unique identifiers to be sure there is a documented chain of custody and safety testing. Before a blood transplant takes place, hospital staff will ‘test’ by mixing the plasma of the patient with red blood cells from the donated blood, making sure the patient’s immune system won’t react to the new red blood cells.

Is there anyone who shouldn’t donate blood?

“Our primary concern is really with the safety of the donor,” said Dr. Rainer. “Our screening questions focus on detecting potential heart and lung issues. People with advanced heart failure are generally not good blood donors, as the volume removed is too much for them to easily handle. Those who have received a heart procedure, such as a stent placement and bypass grafts, are recommended to wait at least six months to donate so that we can see how well they healed.”

Those who are prone to anemia may want to avoid donating blood, and those who have been treated for blood cancers like leukemia or lymphoma are usually asked not to donate. This is because blood donation can be hard on their bone marrow, and it’s harder for them to recover from the donation process.

Most people who have been treated for cancer are able to donate blood but are asked wait one year after all their treatment has stopped to allow their body to recover and make sure they are cancer free. 

Those who have traveled into areas prone to malaria are usually asked to wait before donating, since it’s difficult to test accurately for potential infection. There are also some restrictions based on whether a person has spent time in a country affected by the Mad Cow disease epidemic.

Can sexual behavior make you ineligible to donate blood?

“What we refer to as ‘risky sexual behavior’ increases the risk of catching a disease that can be spread through a blood transfusion,” said Dr. Rainer. “Regulations around donating blood changed radically after the HIV epidemic began in the 1980s, but there have been some recent changes to our screening questions that take into account whether or not someone is in a monogamous relationship, whether or not they’ve recently had new sexual partners within the past four months and other potential risk factors.”

Having engaged in certain sexual behaviors doesn’t make you ineligible for life. Dr. Rainer noted that generally, blood donation centers suggest that those who have had a sexual encounter with a new partner within the last four months do not donate blood.

“We discourage people from using the blood donation process as a way to be tested for infectious disease,” said Dr. Rainer. “While our testing system today is good, it’s not foolproof. The donated blood is intended to go to another person, and we ask that those looking to test for infectious disease seek out the health department, their physician or a clinic in order to get tested instead.”

How old do you have to be to donate blood?

Blood donors need to be at least 16 years old.

What is the difference between donating blood and donating plasma?

“Donating blood will result in a product that will be used for transfusion for red cells, plasma products or platelets,” said Dr. Rainer. “This usually means the product used will be close to what came out.  Donating plasma, on the other hand, will result in a product that is used to make things like albumin, immunoglobulin concentrate and RhoGAM to prevent formation of antibodies.”

Plasma donation is very similar to platelet donation, where only the liquid part of your blood is removed. 

The most widely known difference between blood donation and plasma donation is that blood donation has historically been a volunteer effort, where donors are not compensated financially. Plasma donors are often paid for their donation with cash.

Recently, blood donation centers have begun to offer gift cards, T-shirts or other incentives, but they do not offer direct cash for donations.

What is donated blood used for? Who does it help?

“I like to say blood gives people a second chance, another day and a better quality of life,” said Dr. Rainer. “We often have people come into our emergency rooms that are bleeding badly due to traumatic injuries like those caused by car accidents, knives or firearms. We sustain them with blood products while trauma surgeons stop the bleeding. Unfortunately, these gravely injured people need a lot of blood, and they need it quickly, which puts a strain on the blood supply that may take days to replenish.”

New mothers with traumatic birth injuries (such as bleeding placenta) or patients suffering from an aneurysm may not be visibly bleeding, but they are often losing a lot of blood internally and require a lot of donated blood to survive.

Dr. Rainer noted that there just are no viable alternatives than blood at this time.

Are there non-emergency uses for donated blood?

“Absolutely! Cancer patients often undergo treatment that suppresses their bone marrow, making them prone to infections, anemia or bleeding due to low platelets,” said Dr. Rainer. “Many of our treatments rely on having this donated blood available to help sustain them through grueling, aggressive cancer therapies. Some patients will even become dependent on chronic transfusions, like those with sickle cell anemia, hemophilia or bone marrow failure.”

Many people may benefit from the use of donated blood after surgery or problems with their GI tract, where they don’t require a transfusion but have lost enough blood that they cannot recover easily or quickly from that loss without some help.

Finally, those who become septic, where they suffer from a severe, life-threatening infection that overwhelms the body’s ability to fight back, will start to bleed overwhelmingly as their stores of platelets and plasma proteins are used up. Using donated blood products buys time for the body to keep working to eliminate the infection.

Donated blood saves lives every single day

“Donated blood, platelets and plasma are life-saving products,” said Dr. Rainer. “I really cannot emphasize enough how much we rely on donated blood products, and how badly we need donors willing to help provide these products.”

Interested in looking into donating blood? The American Red Cross and the more locally-based Blood Connection maintain lists of blood donation centers in South Carolina.