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Donating Blood

Donating Blood


Blood donation means giving some of your blood so that it can be used to help someone else. Donated blood helps people who have lost blood in an accident. It also helps people who have an illness such as cancer, anemia, sickle cell disease, or hemophilia.

If you donate blood before you have surgery, your own blood will be kept for you in case you need a blood transfusion. If you don't need it, your blood may be donated to someone else.

Donated blood includes red blood cells and the other things that make up the blood, such as platelets and plasma. Blood that contains all the parts is called whole blood.

You can donate blood at American Red Cross clinics or other clinics or blood banks. You may be able to donate during blood drives at your workplace.

When you donate whole blood, you give about 1 pint (473 mL). It takes about 10 minutes. The whole process—including answering questions and having a short exam—takes up to an hour.

Donated blood is tested to make sure that it's safe to use. It's also checked for its type. This makes sure that the person who needs blood gets the right type.

Who Can Donate

To donate blood, you must:

  • Be at least 17 years old. (In some states, you can donate if you are 16 years old and get permission from a parent.)
  • Weigh at least 110 lb (50 kg). If you are under 18 years old, you may need to meet a certain height and weight measurement.
  • Be in good health.

Some people can't donate because of health or other issues. For example, you may not be able to donate if:

  • You recently donated blood or a blood product. The length of time you must wait between donations depends on the product you are donating, such as whole blood or platelets.
  • You don't have enough hemoglobin in your blood. Before you donate, you will have a test to check your hemoglobin level.
  • You are pregnant.
  • You have traveled to certain countries.
  • Your blood pressure is too high or too low. Your blood pressure will be checked before you donate.
  • You take certain medicines.
  • You have certain health problems, such as HIV.
  • You had a recent needlestick or got a tattoo or piercing.

Having a long-term illness, such as diabetes, doesn't mean you can't donate. You may be able to give blood if your health problem is under control. But you shouldn't donate blood if you feel like you're getting a cold or the flu.

Before you donate, a health professional will ask about your current and past health to make sure that you can donate. Some of these questions are very personal, so you will be asked them in private. You will be asked these questions every time you give blood, because the list of who can give blood may change, or your health may change.

Your body will replace the lost fluid in 24 hours. (It takes a few weeks to replace red blood cells.) You will have to wait 56 days before you can give whole blood again.

How to Prepare

You can do a few things before you give blood to make sure that you have a good experience:

  • Make sure you feel good. Don't give blood if you feel ill.
  • Eat foods rich in iron, such as meat, fish, beans, or leafy green vegetables, a few days before you donate.
  • Eat a healthy meal. But avoid fatty foods. They can affect some of the tests done on donated blood to make sure it's safe.
  • Drink plenty of fluids, especially the day before you donate.
  • Get plenty of sleep the night before.
  • Plan to wear a shirt with sleeves that you can roll up above your elbows.

Learn more

How It Is Done

You will fill out some forms and answer questions about your health.

A health professional will measure your temperature, pulse, and blood pressure. They also will use a finger-stick test to make sure that you have enough hemoglobin in your blood.

The health professional will clean the arm you will use to give blood. Then they will put a needle into a vein on the inside of your elbow. The needle is attached to a bag to collect the blood. You will probably feel a quick pinch when the needle goes in.

You may be given a soft ball or another object to squeeze every few seconds to help the blood flow.

When the bag is full, the health professional will take out the needle. You will get a bandage wrapped around your arm to stop any bleeding.

What Happens After Donation

You have just had some blood removed. This procedure is called phlebotomy (say "fleh-BAW-tuh-mee").

People have their blood taken (drawn) for several reasons. You may have just donated blood so that it can be used to help someone else. Or you may have had blood removed to treat a medical condition, such as hemochromatosis or polycythemia. These take more blood than the sample that is needed for simple lab tests. For donation, about a pint of blood is drawn. If it's drawn for treatment, then more or less than a pint may be taken.

The puncture wound caused by the poke from the needle for giving blood usually heals without trouble. Most people feel fine after they give blood. But there are some simple things you can do to take care of yourself before you go home.

  • Right after you give blood, you may be asked to sit for a while and have some water or juice and a snack.
  • When you leave, get up slowly to make sure that you're not lightheaded. You may want to have a family member or friend take you home.

Self-care after donation

  • In the hours after you give blood, make sure to:
    • Drink plenty of fluids to help replace the lost fluid. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.
    • Limit your physical activity for several hours.
  • If you feel a little lightheaded, lie down for a while, and have some snacks. Call the blood bank or clinic if you feel sick within 24 hours after you give blood.
  • Eat foods rich in iron, such as meat, fish, beans, or leafy green vegetables, for several weeks to help your body make new red blood cells.


Donating blood is safe. You cannot get HIV from donating blood. The needle and bag used to collect blood are sterile and prepackaged. A new package is used every time.

You may have a small bruise on your arm. In rare cases, a person's arm may bleed after the bandage is taken off. If this happens, raise your arm and put pressure on the needle site for several minutes.

Some people may feel faint after they donate blood. This may happen for younger people and for people who are donating for the first time. If you have fainted after donating blood and you choose to donate again, be sure to tell the person who is going to draw your blood. Drinking extra water before you donate may reduce this risk.

Testing Donated Blood

Almost all of the blood used for blood transfusions is donated by volunteers.

The process of blood donation and the handling of donated blood in the United States is regulated by the U.S. Food and Drug Administration (FDA). The FDA enforces five ways to protect the blood supply from disease.

Donor screening.

To donate blood, you must answer questions about your health history, any travel to countries where certain diseases are common, and any behavior that increases your risk for certain diseases, such as drug use or unprotected sex. To be sure you are in good health to donate, your temperature, blood pressure, and the protein in your red blood cells (hemoglobin) are checked. You may not be allowed to donate blood if any of these screening steps suggests a problem.

Deferred-donor lists.

Organizations that collect blood must keep lists of people who are permanently prevented from giving blood. Potential donors must be checked against this list.

Blood testing.

After donation, every unit of blood is tested for certain diseases. These include hepatitis B and C, HIV, West Nile virus, syphilis, and HTLV-I/II viruses. If any disease is found, the blood is thrown away.


Donated blood is kept isolated from other blood. It can't be used until it passes all required tests.

Quality assurance.

Blood centers must keep careful records of all donated blood. If there is a problem, the blood center must tell the FDA and work with them to correct the problem.

Learn more


Related Information


Current as of: September 8, 2022

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Brian Leber MDCM, FRCPC - Hematology

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