In our cells, iron is bound to proteins to form complexes called ferritin and hemosiderin. The main storage protein is ferritin which is found predominantly in the liver.  Ferritin is also found in the spleen, bone marrow and muscle cells. As some ferritin is found circulating in the blood, it forms the best indicator of the amount of iron stored in the body.
Ferritin is critical in keeping the amount of iron in the body balanced (homeostasis). Iron is needed for several critical processes within cells and ferritin makes sure it is available for them. Increasing research has shown that iron has a role in many conditions in the body too including inflammatory, malignant conditions such as cancer and neurodegenerative diseases. 
A low blood ferritin result indicates iron depletion and can be a marker for iron deficiency anaemia. Other conditions such as Hypothyroidism (underactive thyroid) and vitamin C deficiency can also lead to iron deficiency and low ferritin levels. 
Ferritin levels may be high because of iron overload which usually occurs over an extended period. This is where there is a large build-up of iron particularly in the heart and liver where it can cause injury. However, increased levels may also be a result of inflammation which may be due to injury, intense exercise or infection. 
If you have reduced ferritin levels due to iron deficiency it can make you feel unwell. Some of the clinical symptoms of iron deficiency anaemia can include:
Anaemia can affect your ability to concentrate and may negatively affect your work performance. This is because there is a reduced transportation of oxygen in anaemia which can have a serious effect on your energy.  The red blood cells are smaller when anaemia is present causing fatigue and breathlessness.
If your ferritin levels are high this could be a sign of iron overload and may be due to an inherited condition known as haemochromatosis. Haemochromatosis or iron overload can cause:
Other causes of increased ferritin levels may be obesity, kidney failure, inflammation, uncontrolled malignancy, chronic liver disorders and rheumatoid arthritis. 
Inflammation can be a cause of raised ferritin levels.  Ferritin may be more indicative of inflammation in overweight or obese people rather than due to iron status. 
Your iron status can be improved or maintained with diet and adequate exercise.
Good sources of dietary iron include:
Plant-based sources of iron such as dark green leafy vegetables, nuts, seed, pulses and fortified cereals may be absorbed better in the presence of vitamin C.  Try eating fortified breakfast cereals alongside a glass of orange juice or swap chips for a jacket potato with a side of green leafy veg – be sure to eat the skin of the potato.
You should also refrain from drinking tea with your meals as this can affect iron absorption. Instead, you should drink it between meals to ensure you absorb iron effectively. 
Both too much and too little iron can influence energy levels and could affect your ability to exercise. Low iron can also influence how well and quickly your muscles repair themselves after exercise.  Iron deficiency anaemia may also be more common in athletic groups and may need iron supplementation. 
All these tests include Ferritin. Select the test that suits your personal needs.
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