This leaflet gives general information about blood tests. There are separate leaflets that describe various specific types of blood test.

Blood cells, which can be seen under a microscope, make up about 40% of the blood's volume. Blood cells are made in the bone marrow by blood 'stem' cells. Blood cells are divided into three main types:

  • Red cells (erythrocytes). These make blood a red colour. One drop of blood contains about five million red cells. A constant new supply of red blood cells is needed to replace old cells that break down. Millions are released into the bloodstream from the bone marrow each day. Red cells contain a chemical called haemoglobin. Haemoglobin is attracted to oxygen and the two substances can bind together. This allows oxygen to be transported by red blood cells from the lungs to all parts of the body.
  • White cells (leukocytes). There are different types such as neutrophils (polymorphs), lymphocytes, eosinophils, monocytes, basophils. They are a part of the immune system and are mainly involved in combating infection.
  • Platelets. These are tiny and help the blood to clot if we cut ourselves.


Tags: blood test, blood cells, blood test report