WHAT IS BLOOD?

Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions, including:

• transporting oxygen and nutrients to the lungs and tissues
• forming blood clots to prevent excess blood loss
• carrying cells and antibodies that fight infection
• bringing waste products to the kidneys and liver, which filter and clean the blood
• regulating body temperature

The blood that runs through the veins, arteries, and capillaries is known as whole blood, a mixture of about 55 percent plasma and 45 percent blood cells. About 7 to 8 percent of your total body weight is blood. An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about nine pints. 

COMPONENTS OF BLOOD

There are four basic components that comprise human blood: plasma, red blood cells, white blood cells and platelets.

Red Blood Cells

Red blood cells represent 40%-45% of your blood volume. They are generated from your bone marrow at a rate of four to five billion per hour. They have a lifecycle of about 120 days in the body.

Platelets

Platelets are an amazing part of your blood. Platelets are the smallest of our blood cells and literally look like small plates in their non-active form. Platelets control bleeding. Wherever a wound occurs, the blood vessel will send out a signal. Platelets receive that signal and travel to the area and transform into their “active” formation, growing long tentacles to make contact with the vessel and form clusters to plug the wound until it heals.

Plasma

Plasma is the liquid portion of your blood. Plasma is yellowish in color and is made up mostly of water, but it also contains proteins, sugars, hormones and salts. It transports water and nutrients to your body’s tissues.

White Blood Cells

Although white blood cells (leukocytes) only account for about 1% of your blood, they are very important. White blood cells are essential for good health and protection against illness and disease. Like red blood cells, they are constantly being generated from your bone marrow. They flow through the bloodstream and attack foreign bodies, like viruses and bacteria. They can even leave the bloodstream to extend the fight into tissue.

ABOUT BLOOD TYPES

Your blood type is inherited and everyone’s blood type falls into one of eight types. The below chart shows the percentage of the population that has each blood type.

Compatibility

Type matters when it comes to blood transfusions. There are very specific ways in which blood types and blood components must be matched for a safe transfusion.

WHY SHOULD YOU DONATE BLOOD

Donating blood regularly has proved beneficial not only for the recipient but also the donor. It is helpful for the vital organs, and it reduces risk for chronic diseases such as cancer and stroke.

Food and medications

Before your blood donation:

• Get plenty of sleep the night before you plan to donate.
• Eat a healthy meal before your donation. Avoid fatty foods, such as a hamburger, fries or ice cream.
• Drink plenty of water before the donation.
• Check to see if any medications you are taking or recently took would prevent you from donating. For example, if you are a platelet donor, you must not take aspirin for two days prior to donating. Talk to your health care provider before you stop taking any medications.
• Wear a shirt with sleeves that can be rolled up.

What you can expect

Before the procedure

Before you can donate blood, you will be asked to fill out a confidential medical history. It includes questions about behaviors known to carry a higher risk of bloodborne infections — infections that are transmitted through blood.

Because of the risk of bloodborne infections, not everyone can donate blood. The following are groups that are not eligible to donate blood:

• Anyone who has used injected drugs, steroids or another substance not prescribed by a health care provider in the past three months
• Men who have had sexual contact with other men in the past three months
• Anyone who has a congenital coagulation factor deficiency
• Anyone who has had a positive test for HIV
• Anyone who has engaged in sex for money or drugs in the past three months
• Anyone who, in the past 12 months, has had close contact with — lived with or had sexual contact with — a person who has viral hepatitis
• Anyone who has had babesiosis, a rare and severe tick-borne disease, or the parasitic infection Chagas' disease

You will also have a brief physical exam. The exam includes checking your blood pressure, pulse and temperature. A small sample of blood is taken from a finger prick and is used to check the oxygen-carrying part of your blood (hemoglobin level). If your hemoglobin concentration is within a healthy range, and you've met all the other screening requirements, you can donate blood.

After the procedure

After donating, you sit in an observation area, where you rest and eat a light snack. After 15 minutes, you can leave. After your blood donation:

• Drink extra fluids.
• Avoid strenuous physical activity or heavy lifting for about five hours.
• If you feel lightheaded, lie down with your feet up until the feeling passes.
• Keep your bandage on and dry for the next five hours.
• If you have bleeding after removing the bandage, put pressure on the site and raise your arm until the bleeding stops.
• If bruising occurs, apply a cold pack to the area periodically during the first 24 hours.
• Consider adding iron-rich foods to your diet to replace the iron lost with blood donation.