Haemoglobin

Doctors often recommend blood tests to obtain accurate information for a diagnosis or to get more details about your current state of health.

A needle and a syringe are used to take blood out of a vein, usually from the inside of the elbow, and the blood is analysed in a laboratory.

A blood count is often the first part of a blood test.  It determines whether the amounts of platelets and red and white blood cells in your body is within the “normal” range.

Some people expect blood to be blue when it comes out of the veins, because it doesn’t have oxygen in it, but in fact, it is dark red.

Blood is never blue. There’s a rare condition which gives it a bluish hue, but even then the overall color is red. Veins appear blue because of the way light is absorbed and reflected by the body and because of the way our brains process color.

The iron in red blood cells gives the blood its colour (Like the way iron, with oxygen, gives rust a reddish color).

Iron’s affinity with oxygen allows red blood cells to carry oxygen through the arteries to all the tissues. The cells then pick up carbon dioxide on their return journey to the lungs.

One of the most important red blood cell tests is used to find out how much iron (which is combined with proteins and called haemoglobin), there is in the blood. If a person suffers from anaemia their haemoglobin level will be less than normal and the amount of oxygen in the body is reduced.

The total number of white blood cells and how many of the different types of white blood cells are present is also counted.  This is called the differential white blood cell count.  White blood cells are involved with immunity, breaking down micro-organisms and fighting infection. More are produced when there is a bacterial infection, bleeding or a burn.

Platelets are also counted. They are used to seal cuts, so a low number of platelets can make a person vulnerable to bleeding and a high number makes blood clots more likely.

Catherine