There are three types of blood cells – red blood cells, white blood cells and platelets.
Red Blood Cells (RBCs or erythrocytes) are the most abundant cells in blood. Normal range of RBC count is 4.5 to 5.5 million cells/cubic mm. They contain haemoglobin, an iron-containing protein, which is responsible for oxygen transportation around the body. Low levels of this blood cell means decreased oxygen supply to the body leading to fatigue and weakness or anaemia. Low levels of RBCs are seen in iron deficiency anaemia, thalassemia, stomach ulcers, sickle cell anaemia and certain cancers. High levels are seen in case of chronic smokers, alcoholics and in people with long-term lung, kidney, heart or liver disease. It may also be increased in cases of dehydration, burns, diarrhoea and vomiting.
White Blood Cells (WBCs or Leukocytes) form part of the body’s immune system and help defend the body against infection. They are characterized as granulocytes or agranulocytes. There are three types of granulocytes – neutrophils, eosinophil and basophils, and two types of agranulocytes – monocytes and lymphocytes. Normal range of WBC count is 4000 – 11000 cells/ cu mm. A value above 11000 is termed as leucocytosis and a value less than 4000 is termed as leucopenia. A slightly elevated count can also be seen in pregnancy or in children below the age of 2 years. WBC counts are high during an infection. A very high count could indicate leukaemia. Increased neutrophil count could indicate a bacterial infection and elevated levels of lymphocytes could indicate a viral infection. Eosinophil levels are increased in allergies or parasitic infection. Low levels of WBCs are commonly seen in people on steroid or cancer medications. Low WBC levels could also indicate a malfunctioning of the bone marrow.
Platelets (Thrombocytes) are cells that help the blood to clot. Normal range of platelet count is 1.5 to 4 lakhs/cu mm. Thrombocytopenia is low platelet count and thrombocytosis is elevated platelet count. An extremely low level of platelets in the body could lead to bleeding. It may be seen in dengue, bone malfunction, cancer chemotherapy, etc. High levels are seen in infections, blood and bone marrow disorders, splenectomy, cancer, etc.