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A woman donating blood

Quiz results: How much do you know about giving blood?

Take a look at the answers below for the facts about blood donation—and why becoming a donor can save lives.

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1. How much blood can one person donate at a time?

One pint

A pint equals 16 liquid ounces, and that might seem like a lot of blood to lose in the 15 minutes it takes to actually donate. But it’s only a tenth of the total amount of blood circulating through your system. Afterward, your body begins to replenish it quickly: Plasma, the largest component of your blood, is replaced within 24 hours, while red blood cells need four to six weeks to regenerate. This is why blood banks require donors to wait at least eight weeks before donating again.

2. What blood type is most in demand?

A cartoon of hands holding a bag of type O blood

Type O

Both O negative and O positive are the most sought after. Though only 7% of the population is O negative, this blood can be used for people with any blood type. The need for O positive is also high because it’s the most common blood type; 38% of the population is O positive.

But just because you aren’t type O doesn’t mean your blood won’t be needed. “The most in demand blood type is the one that best matches a patient who needs it in that moment,” says Jennifer Cole, a leader in Supply Chain Strategy Planning and Operations who also volunteers with Johnson & Johnson Blood Drive Services.

3. True or false: Everyone can donate blood


The vast majority of people in the U.S. are eligible to become whole blood donors, but some restrictions apply. For starters, there are age and weight requirements: Donors must be at least 16 years old and weigh 110 pounds, according to the American Red Cross.

Health status matters as well. People with certain infectious diseases, such as HIV or hepatitis B or C, are also ineligible, as are survivors of blood cancers (like lymphoma or multiple myeloma). And if you’ve traveled to a malaria-risk country, you’ll need to wait at least three months before you’re cleared to donate.

Having a new tattoo can also temporarily block you from becoming a donor—if you got inked in a state that doesn’t regulate tattoo parlors, like Georgia, Idaho, Maryland, Massachusetts, New York, Pennsylvania and Wyoming. If you were tattooed in one of these states, you must wait three months from the date you got the tattoo before donating.

For a rundown of more specific information on what could or can’t bar you from becoming a donor, click here.
4. Donated blood is in shortest supply which times of year:

Summer icon and winter icon next to one another

Summer and winter

The biggest drops in donor blood amounts happen during the winter and summer holidays. During parts of winter, “people are away on vacation; also, many blood drives are held at high schools or colleges, and during this time students aren’t there to give,” points out Cole.

Demand for blood also rises in the summertime, just when many people are planning vacations and not thinking about donating. “There tend to be more ER traumas during the summer months, and many people schedule elective surgeries at this time, when work is quieter,” Cole adds.

5. What blood components can be donated?

Bags filled with donated blood

Blood cells, platelets and plasma

Blood donation is a collective term, but there are actually four different types of donations involving various parts of blood. Whole blood donation is a term that encompasses every component of blood: red cells, white cells and platelets, suspended in plasma. Whole blood donation can be done every eight weeks.

“Power red” donation means you give a concentrated dose of red cells, which are typically used for trauma patients, people with sickle cell disease, newborns and emergency transfusions during birth. This kind of donation can be done up to three times a year.

Platelet donation most often benefits cancer patients. Platelets are cell fragments that help stop bleeding, and some cancer treatments decrease a person’s natural ability to produce them. You can donate platelets every seven days.

Finally, donations of plasma—the fluid that carries these other blood components through the bloodstream—are typically used to treat patients in emergency situations. Plasma donation is only permitted every 28 days.

Not all blood donation types are done at individual blood drives, so check ahead before you make your appointment.

6. How many lives can one blood donation potentially save?

Bathroom sign icons on a green background


That might sound like a surprisingly high number, but remember, each blood donation equals a pint of blood—which can be transfused into a single person or multiple people. Whole blood can also be separated into platelets, plasma and red blood cells, then given to different people who have varying needs.

7. After donating blood, you might experience this side effect:

Feeling faint

Though not everyone experiences it, feeling faint, lightheaded or even a little dizzy is a normal response after giving blood. It’s why many blood donation sites typically invite donors to sit for a while in a recovery area and offer a drink and snack, like water and cookies, to help replenish their energy before heading home or back to work.

Drinking plenty of fluids post-donation can also minimize feeling faint. The American Red Cross recommends consuming an extra 32 ounces of liquids (like water or juice—but not alcohol, which you should avoid) over 24 hours following donation.

Other potential side effects include fatigue, as well as bruising or slight bleeding at the site where the needle was inserted into your arm. These symptoms shouldn’t be more than a little bothersome and will clear up quickly. But if they become severe, contact a doctor ASAP.

8. True or False: You can find out where your blood goes after you donate

A smart phone with text that says Follow Your Blood Donation's Journey"


If you donate blood at a donation center or blood drive sponsored by the Red Cross, you can download the Red Cross app. The app shows you the journey your blood takes once it leaves your system: from the testing stage (where it’s typed and then screened for the presence of infectious diseases) to where it’s stored to the day it is transfused into a patient.

“You’ll be able to actually see what hospital it ends up in, and some sites even let you know what your blood is used for: for example, to treat a cancer patient, or for a trauma victim,” says Cole. This way, you can see firsthand how your blood was used to save lives.

If you donate at a site affiliated with another blood donation organization, you can probably still track that journey. “Other blood centers have apps as well, or they have different programs to let you know where blood goes,” explains Cole, for example, via a QR code you can scan. “When you donate, ask the blood center how you can track your donation,” she adds.

How to find a blood donation site near you

The American Red Cross is one of Johnson & Johnson’s partners to promote blood donation. Type your ZIP code into this Red Cross link for a blood drive or site in your area.

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