Blood is the red colored fluid flowing continuously in the human body’s circulatory system. On an average, a human being has about 5-6 liters of blood flowing in the body. About 7% of the body weight of a healthy individual is accounted for by blood.

Blood mainly contains a fluid called plasma which has three types of cells - Red Blood Cells or RBC’s, White Blood Cells or WBC’s and platelets. Plasma acts as a vehicle to carry nutrition including protein, glucose, enzymes, and hormones etc; Red blood cells carry oxygen from the lungs to various body tissues; White blood cells help the immune system of the body and platelets facilitate the process of clotting and coagulation of blood.

The RBC, granulocytes of WBC and platelets are produced mainly by bone marrow. The lymphocytes and monocytes are formed in the lymphoid and reticulo-endothelial tissues. The orderly proliferation of the cells in the bone marrow and their release into the circulatory system is carefully regulated according to the needs of the body. Every day, new blood cells are produced in the bone marrow and every day old cells die and are removed from the body.

Red blood cells have a life of about 120 days, white blood cells live for a few days and platelets for a few hours. The addition of new cells and removal of old cells is a continuous process.

Haemoglobin is a substance present in the red blood cells. It helps in carrying oxygen and carbon dioxide to different parts of the body. On an average, the haemoglobin level for a healthy male should be between 14 - 16 gm % and for a female between 12 - 14 gm %.

Every individual belongs to two major types of blood groups. The first is called the ABO  group and the second type is called the Rh - group. In the ABO - group there are four categories namely: A Group, B Group, O Group and AB Group. In the Rh - group either the individual is Rh-positive, or Rh-negative. Rh denotes the Rhesus factor, named for Rhesus monkeys.

Thus every human being belongs to one of the following groups.

AB positive or AB negative

The positive or negative aspect is based on the Rh factor

For all practical and routine purposes, it is ideal to transfuse to the patient the same group of blood which he/she belongs to. Under no circumstances can an O group person get any other blood except O. Similarly, an A group patient cannot be given B group blood and vice versa. It is only in a dire emergency that we take O group as a universal donor and AB groups as universal recipient.

The blood of an A group person contains anti - B group antibodies. In those with B group blood, there are anti – A group antibodies. If we give A group blood to a B group patient, it is bound to be incompatible and will result in serious consequences.

A patient with Rh-negative blood cannot be given Rh-positive blood as the antigen-antibody reaction will result in severe consequences. In cases where a woman is Rh negative and her husband is Rh positive, the first child with Rh positive may be normal. But, subsequently, the woman may not conceive or may have repeated abortions. There may be intra-uterine fetal death. If the child born is alive, it will suffer from a fatal disease called “Erythroblastosis Foetalis”. Now, mothers can be given an injection of anti-D within 24 hours of the delivery of a Rh-positive child and thus protect the next baby from this catastrophe.

Blood is collected in plastic bags that contain in liquid chemical which prevents blood from coagulating. On an average, about 450 mL of blood is collected from a person. This blood, plus the amount of anticoagulant present in bottle or bag, is known as one unit of blood.

Whole blood can be stored for up to 35 days, when kept in CPDA anti- coagulant solution and refrigerated at 2 - 4oC.

Several components from blood can be separated and used to treat specific conditions. This helps in utilization of one unit of blood for several patients. These components are : Packed RBCs, Fresh Frozen Plasma, Platelet Rich Plasma, Platelet Concentrate, Cryoprecipitate, Factor VIII and IX, Albumin, Globulin and many others. Now, with the advent of cell-separater machines a particular component from the donor can be collected while blood circulates through the machine and rest of the blood constituents go back to the donor.

There are many situations in which patients need blood to stay alive:

• A patient needs blood after a major accident or surgery in which there is loss of blood.
• On an average, for every open heart surgery, about six units of blood is required.
• After a miscarriage or childbirth, the patient may need a large amount of blood to be transfused for saving her life and also the child’s.
• For patients with blood diseases like severe anaemias, leukaemias (blood cancer), haemophilia (bleeding disorder), thalassemia etc. repeated blood transfusions are the only solution.

In many other situations like poisoning, drug reactions, shock and burns, blood transfusion is the only way to save precious human life

Yes. All blood units are tested for HIV, hepatitis B, hepatitis C, syphilis, etc. Only those units of blood are transfused which are free from these infectious markers.

There are three types of blood donors:

1. Professional blood donors - They sell their blood, which is of very poor quality and can transmit very dangerous diseases to the recipient.
2. Replacement blood donors - Healthy relatives and friends of the patient give their blood, of any group, to the blood bank. In exchange, the required number of units of the required blood group is given to the patient.
3. Voluntary blood donors - Here, a person donates blood voluntarily. The blood can be used for any patient without divulging the identity of the donor. This is the best type of blood donation where a motivated human being gives blood in an act of selfless service.

Usually, any person within the age group of 18 - 60 years with a minimum body weight of 45 kgs, and having a minimum haemoglobin content of12 gm% is eligible to donate. However, all countries have criteria for blood donation in their respective countries.

Nothing special. The donor should eat at regular meal times and drink plenty of fluids.

The procedure is done by skilled, specially trained technicians and takes three to eight minutes. However, from start to finish (filling form, post-donation rest etc.) the entire process should take around 30 minutes.

No. Only the blood of a human being can be transfused to a human.

Absolutely not. Rather a donor after having given blood voluntarily gets a feeling of pleasure and peace. Within a period of 24 - 48 hours, the volume of blood donated is again formed in the body.

Not really. After resting for a while, the donor is given something to drink. It may be a cup of coffee or milk or fruit juice alongwith a few biscuits or fruit. The donor needs no other special diet. A routine, balanced diet is adequate.

The body replaces blood volume or plasma within 24 hours. Red blood cells need about four to eight weeks for complete replacement.

A three-month gap between donations is a very safe interval.

Of course! Routine work is absolutely fine after the initial rest. Rigorous physical work should be avoided for a few hours.

Yes, if the donor has suffered from any of the under-mentioned diseases: - Fever: The donor should not have suffered from fever for the past 15 days.

Jaundice: A donor should not have tested positive for hepatitis and suffered from jaundice.

Blood transmitted diseases: Syphilis, malaria, filaria etc. debar a donor from donating blood until treatment is over and the donor is disease-free.

Drugs: If a person is taking drugs like aspirin, anti hypertensives, anti-diabetics, hormones, corticosteroids etc., he/she is unfit to donate blood. No HIV-positive person can be allowed to donate blood.

Yes, blood donation is a noble, selfless service! It gives the donor a feeling of joy and contentment. Also it is an expression of love for mankind, as blood knows no caste, colour, creed, religion or race.