What is blood?

Blood is a bodily fluid which is circulated around the body via small vessels. Blood contains nutrients and oxygen which are needed to maintain healthy tissues. Blood has a number of components, including red blood cells, white blood cells, plasma, and platelets.

For more information, please see our anatomy article on Blood – Function and Composition.

When do people need blood?

There are many reasons why people may need extra blood that has been donated from others. If a person needs blood, then it will be received via a process called blood transfusion. The donor blood will be matched to the patient’s and then transfused using an injection in a vein of the arm.

For more information on transfusion, please see our treatment page on ‘Blood Transfusion.’

A blood transfusion may be needed for the following conditions:

ABO blood typing system

In 1901, Austrian Karl Landsteiner discovered the human blood groups. Today these are used to ensure that blood transfusions are safe for patients. If two blood groups are mismatched, then this can cause clumping of the blood (agglutination), which can be fatal. Blood groups are determined by the presence of certain types of protein (called antigens) on the red blood cells.

There are four different blood types: A, B, AB or O.

Individuals with O blood do not have antigens on the surface of their red blood cells. For this reason, they are called the universal donor. A person who receives an O type transfusion is unlikely to reject the blood. A person with AB blood is called the universal recipient, because they can safely receive blood from any of the other types.

In Australia, type O blood is the most common, followed by A, then B, with AB the least common of all. Blood donations of all types are always needed.

For more information, please see our anatomy article on Blood Types.

Rhesus system

The rhesus system is a way to further classify blood. For example, two people may have type O blood, but differ according to the Rhesus system. For the type O+, the O indicates the ABO system, whereas the + indicates a positive Rhesus factor (Rh). The Rh factor is another protein found on the surface of red blood cells. A person either has this protein or they do not. This means a person must either be Rh negative or positive.

For more information, please see our anatomy article on Blood types.

Who can donate blood?

In Australia, blood donation is organised and regulated by the Australian Red Cross Blood Service, who can be contacted on 13 14 95. Their website includes comprehensive information about blood donation and is available at http://www.donateblood.com.au/.

The health and safety of blood donors is a prime concern. For this reason, some people are not eligible to give blood because it could jeopardize their own health. This includes people who are:

  • Under 16 or over 70 years of age
  • Are pregnant
  • Have recently given birth
  • Weight less than 45 kg (or 50kg for 16 and 17 year olds)
  • Have low blood pressure
  • Have a heart condition
  • Have been to the dentist recently
  • Have a cold or flu
  • Have had a tummy upset in the last week
  • Have recently been to the dentist

Some people may also be excluded from giving blood because it would pose a risk to recipients. For example, people who have had tattoos recently are unable to donate because unsterile needles used during the procedure carry a risk of infection with blood borne diseases. People who lived in the United Kingdom (UK) for more than six months between 1980 and 1996 are also excluded because they may have been exposed to Creutzfeldt-Jacob Disease (CJD) through contaminated meat.

There are many other reasons why a person may be unable to donate blood, especially if an illness is very recent. Blood is more likely to be accepted by the Red Cross if the donor is feeling healthy and well. A detailed medical history will be taken during the blood donation appointment. However, you should not assume that you are unable to donate blood. In many cases, it will depend on the circumstances. Some medical conditions will not preclude you from donating blood if they pose no risk to the recipient.

Why should I donate?

For many people with serious illnesses, a blood transfusion is the only effective treatment available. In Australia, donors are not paid for their blood. This means that the Red Cross Blood Service relies on the altruism and generosity of a small group of Australians. For several years now, the donation rate has been alarmingly low at only 3% of the population. It is important to encourage people to donate for the first time. However, it is equally important to increase the number of people who go on to become regular donors.

Most people who donate appear to be motivated by the opportunity to save lives. Blood donation is a simple way to make an enormous difference. Donors will never know who received their blood, but the recipients will be forever grateful. Other people may want to donate because they realize that they may be in the position of needing blood one day. By putting yourself in the shoes of a person awaiting a transfusion, it is easier to empathise with people who rely on blood products for survival.

Another reason why it is important for people to donate regularly is because blood has a short shelf life, and therefore cannot be kept forever. This means that the Blood Service in Australia needs 20,000 donations per week just to maintain supplies. Platelets last only 5 days and red blood cells last for 42 days at the most. Secondly, a range of donors is needed to ensure that there are blood matches for recipients. Sometimes the Blood Service may have particularly low stocks of a certain blood type. Blood donations are tested for diseases that could be passed to the recipient, such as HIV, Hepatitis B, Hepatitis C and Syphilis.

Finally, blood donation is an easy procedure which carries very few risks to the donor. The staff at blood donation centres are very grateful to those who take the time to give blood. As such, the staff always ensure that donors are comfortable, and usually offer refreshments to make the experience enjoyable. Some people even find that donation is a relaxing escape from the pressures of work.

Blood donation types

Some people only require certain components of blood to be transfused. This means a single donation of whole blood can potentially save 3 lives. Whole blood donations are needed for people who experience severe blood loss during surgery, or due to a serious accident. People who choose to donate whole blood can donate every 12 weeks. An apheresis donation is one where only plasma or platelets are donated. This means the red blood cells are returned to the donor. People who choose to donate in this way can return sooner, after about 2 or 3 weeks.

Common side effects

Blood donation is known to be a safe procedure. However, donors may experience some minor side effects, including:

  • Dizziness or feeling light headed
  • Bruising where the needle was inserted
  • Fatigue

Please note that donors are advised to take it easy after giving their donation. Refreshments are provided at Red Cross Blood Services. Donors should also avoid doing any strenuous activity with the arm that they used to give the donation.

How can I donate blood?

The first step is to visit the Red Cross Blood Service website to find your nearest blood donation centre. You can then make an appointment by calling 13 14 95. Donors are advised to eat a substantial meal before their appointment, and to have 3–4 glasses of water, fruit juice or milk. Donors are also required to bring identification that includes 3 details such as name, date of birth, address, signature or photo.



  1. Who needs blood? [online]. Australian Red Cross Blood Service; 2008 [cited 22 January 2008]. Available from: [URL link]

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