What is blood?

Blood is made up of several elements, each of which performs a special function in the body.

• Red blood cells carry oxygen from the lungs to all other tissues in the body. From the tissues they pick up carbon dioxide that is carried back and released into the lungs.

• White blood cells are one of the body's defenses against disease. Some cells travel throughout the body and destroy bacteria and virus, and other help fight against malignant disease.

• Platelets are specialized cells that plug damaged blood vessel walls and join other elements in the blood in the production of clots to stop bleeding.

• Plasma is a yellow fluid made up of about 92% water and 7% vital proteins such as albumin, gamma globulin, and antihemophilic and other clotting factors. The remainder consists of mineral salts, sugar, fats, hormones, and vitamins.

Red blood cells, white blood cells, and platelets account for about 45% of the volume of blood in the body. The remaining 55% is plasma.

Who can donate blood?

Most healthy people age 17 or older who meet basic donor criteria can give blood every eight weeks.

What happens during the donation process?

Giving blood is easy and takes a little over an hour. The process includes registering, giving a brief medical history, and having temperature, blood pressure, and hemoglobin checked. The actual donation takes less than 10 minutes and is relatively painless. Afterwards, you are invited to have some light refreshments to help restore body fluid levels.

Can I participate in regular activities after donating blood?

For the most part, yes. You may return to work although you should avoid strenuous activities. You should avoid heavy exercise or lifting for at least 5 hours after donating and drink plenty of fluids for the next 24 hours.

I play on a sports team. Can I practice or compete right after donating blood?

When you give blood, you temporarily lose some fluid which your body replaces within several hours. It is not a good idea to practice vigorously or compete right after giving blood - you could get dehydrated. If you intend to compete the day of your blood drive, do not give blood. If you must practice after donating, take it easy and use common sense.

How often can I donate blood?

You may donate whole blood once every eight weeks. Federal regulations preclude us from collecting whole blood from a donor sooner than eight weeks after a prior donation. It is important that donations are not made more frequently. Regulations may be different for those giving blood for themselves (autologous donors). We urge people to donate as often as they are eligible.

Can you donate blood for yourself?

An autologous donation is one in which you donate blood for yourself before having surgery. Your own blood is the safest and best match for you. Red Cross encourages autologous donations for elective surgery. Contact your doctor first to find out if you can donate blood for yourself.

Usually, people who need blood won't know in advance. Donating blood for yourself and freezing it for use in an emergency is impractical. The frozen blood would need to be thawed and prepared for transfusion which would take several hours. It is unlikely that such blood could be available to you in a life-threatening situation.

What does it mean to be a "deferred" donor?

A donor may be deferred (asked not to give blood) for a number of reasons. For example, if a potential donor is ill or anemic on a particular day, he/she is deferred. This donor may return another day to donate.

A donor is deferred indefinitely when blood tests show exposure to one of several infectious diseases such as HIV or hepatitis. Deferred donors are entered into a national computer registry, and the donor is asked not to donate again. Blood from these individuals will not be accepted at any Red Cross donor site.

What is a rare donor?

Your blood contains red blood cells, and on the surface of these cells are markers called antigens. Red cells carry many different antigens. The most familiar are those of the ABO (A, B, AB, O) blood group. Whether you have a certain blood type depends on whether or not your red cells have particular antigens.

There are some antigens that most of us carry on our red cells but that a few people's red cells lack. A rare donor is one whose blood lacks antigens that most people have. If only one person in 1,000 or more people lacks the same antigen as you do, then your blood type is considered "rare." If only one in 10,000 or more people lacks your antigen, your type is considered "very rare."

The Red Cross wants to make sure that rare blood is available for anyone in need. That is why Red Cross asks everyone with a rare blood type to join the Rare Donor Registry.