Haemoglobin is a protein which is found in red blood cells and is responsible for carrying oxygen to other cells in the body from the lungs. Measuring the amount of haemoglobin present in the blood gives a good indication of how well the blood is carrying oxygen around the body.
Haemoglobin is an oxygen-carrying protein found in all vertebrates except fish. It makes up around 96% of the dry weight of red blood cells and contains iron which is needed to bind haemoglobin to oxygen. Haemoglobin is made up of four heme molecules each with a iron ion. Each iron ion (Fe2+) can bind with one molecule of oxygen. Oxygen bound haemoglobin is known as oxyhaemoglobin and when it reaches a cell which has little or no oxygen, the oxygen dissociates from the haemoglobin and enters the tissue.
A low haemoglobin concentration can be a sign of iron deficiency anaemia. Iron deficiency can be absolute: when total body iron stores are low or completely used up, or functional: when iron stores are normal or increased. Functional iron deficiency usually occurs when inflammation occurs. Iron is an essential component of haemoglobin and is also needed for other functions within the cell. Several mechanisms can contribute to the development of iron deficiency such as diet, menstruation and medications.
Below average haemoglobin levels can be caused by vitamin deficiencies such as vitamin B12, kidney disease, infections, bleeding, inherited conditions and liver cirrhosis.
Above average levels of haemoglobin can also be a sign of dehydration, lung disease or your bone marrow may be producing too many red blood cells (polycythaemia).
If a below normal or a low haemoglobin result is caused by iron deficiency it can produce the following symptoms:
Anaemia can also have a negative effect on physical performance including work productivity. In older people, anaemia has been linked with cognitive decline. This is also true if iron deficiency occurs in the womb. Even after birth, the child can experience cognitive abnormalities which may affect their normal development and even cause psychiatric illness.3
Polycythaemia can be a cause of abnormally high levels of haemoglobin in the blood. This is where there is an increase in red cells produced by the bone marrow. Polycythaemia is rare but is caused by a genetic mutation. Symptoms can include:
Dehydration can also cause a high or above-normal haemoglobin level. Although thirst is a symptom, other symptoms can make you feel quite unwell including fatigue, feeling dizzy, dry mouth, lips and tongue. Dehydration can also influence your mental status, too. Malnourishment can also cause these symptoms. In which case, your energy levels will be low, and you may not have the desire to carry out your usual daily activities.
Iron is essential for the function of red blood cells, without it or a lack of it the red cells can become compromised leading to health complications. Leading a healthy lifestyle can help to keep your blood cells healthy and functioning optimally.
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.
You should ensure you are adequately hydrated. Tea, coffee, squash and fruit juice can all help to keep you hydrated.
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.
Always keep yourself well hydrated during exercise with water and isotonic drinks.
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 Lab Tests Online UK. (2018). Haemoglobin. Available at: https://labtestsonline.org.uk/tests/haemoglobin
 Panawala, L. (2017). What is the Function of Hemoglobin in the Human Body. Pedia. Available at: https://www.researchgate.net/publication/313841668_What_is_the_Function_of_Hemoglobin_in_the_Human_Body
 Lopez, A., Cacoub, P., Macdougall, I, C and Peyrin-Biroulet, L. (2015). Iron Deficiency Anaemia. The Lancet.
 McMullin, M, F., Wilkins, B, S and Harrison, C, N. (2015). Management of Polycythaemia Vera: A Critical Review. British Journal of Haematology: 172(3).
 National Health Service. (2017). Dehydration. Available at: https://www.nhs.uk/conditions/dehydration/
 British Dietetic Association. (2017). Food Fact Sheet: Iron. Available at: https://www.bda.uk.com/foodfacts/iron_food_fact_sheet.pdf
 Lane, D, J, R and Richardson, D, R. (2014). The Active Role of Vitamin C in Mammalian Iron Metabolism: Much More than Just Enhanced Iron Absorption. Free Radical Biology and Medicine: 75, pp 69-83.
 Zijp, I, M., Korver, O and Tijburg, L, B, M. (2000). Effect of Tea and Other Dietary Factors on Iron Absorption. Critical Reviews in Food Science and Nutrition: 40(5), pp 371-398.
 Beard, J and Tobin, B. (2000). Iron Status and Exercise. The American Journal of Clinical Nutrition: 72(2), pp 594S-597S.