Anaemia occurs when you have an abnormally small amount of red-blood cells. These cells contain haemoglobin, a red pigment that gives blood its colour.
The haemoglobin carries oxygen around the body. When the haemoglobin is low, blood is unable to supply the body's tissues with enough oxygen. Symptoms include tiredness, weakness and in severe cases, fainting. Treatment depends on the cause of the anaemia. It is usually simple and may require improving the diet or taking supplements. If the cause is vitamin B12 deficiency, your doctor may prescribe vitamin B12 injections.