July 21, 2020

What is Iron?

Iron is an important nutrient within the human body. However, iron metabolism disorders are amongst the most common diseases in the human body.[1] It is needed to form haemoglobin in red blood cells. Haemoglobin is responsible for transporting oxygen around the body to cells and tissues which need it. Because the body is unable to make its own iron, we must get it from dietary sources. Low levels of iron can lead to anaemia, whereas too much iron can be toxic, so a fine balance must be achieved.

The body absorbs iron from food in the small intestine and travels around the body bound to the transport protein, transferrin. Approximately 70% of the transported iron makes up haemoglobin in our red blood cells, while most of the rest is stored in the tissues as ferritin or haemosiderin.  Small amounts of iron are also used to produce other proteins and some enzymes.[2]

Why take an Iron blood test?

An iron blood test usually looks at the amount of iron in the body using several substances in the body like transferrin and ferritin. The test can help to establish whether your iron levels are within the normal range or if there is evidence of deficiency or overload.

You can test your iron levels by purchasing a simple at-home finger prick test kit which is then analysed at an accredited lab. Forth offers a number of blood tests which include iron markers such as our best-selling Baseline Plus health check or our Nutri-check test.  An iron blood test is also available in some of our bigger blood test profiles such as Vitality which tests over 30 biomarkers integral to good health.

What function does Iron have in the body?

The main function of iron in the body is to help produce healthy, functioning red blood cells. Iron makes up part of haemoglobin, the protein present in red blood cells responsible for transporting oxygen around the body. Most of the iron within the body is found in haemoglobin.

Iron is also present in another molecule, myoglobin. Myoglobin is like haemoglobin but is found in the muscles, it’s what gives red meat its distinctive colour. There are different types of muscle fibre, including red and white. The amount of each fibre present will determine the colour of the meat. Red muscle fibres are present in muscles which are needed for long periods of activity. There may be fat stored around these muscles which can be used as a source of energy. The oxygen needed to combine with the fat to produce the energy is supplied by the myoglobin. Myoglobin gets its oxygen from haemoglobin in the red blood cells. Therefore, myoglobin is responsible for delivering oxygen to the muscles to keep them working.[3]

How do changes in Iron affect health and wellbeing?

Both high and low levels of iron can have negative health consequences on the body. There are inherited conditions like hereditary haemochromatosis which increases the absorption of iron, leading to a build-up of iron in the tissues causing organ damage. Damage can be caused to organs such as the liver, heart, pancreas, pituitary gland and the skin.

Another cause of increased iron levels is iron overload, a condition which causes the body to store excess iron and deposits it in various organs throughout the body.[4]

Low levels of iron, however, can lead to iron deficiency and anaemia. There are several factors which can cause iron levels to be low. It is possible for there to be no physical symptoms during the early stages of iron deficiency. However, as the condition progresses it can cause symptoms which are uncomfortable and may affect your ability to carry out everyday tasks.

If you are worried about your iron levels or just want to check where you fall on the range, you can test your iron level with Forth’s leading blood test service.

What can cause Iron to change?

Common causes of reduced iron levels are:

A reduced iron level may be caused by:

  • Inadequate iron intake
  • Bleeding
  • Stomach ulcers
  • Piles
  • Some medication like non-steroidal anti-inflammatory drugs (NSAIDs)


What are the most common symptoms of Iron Deficiency?

The common symptoms of iron deficiency anaemia are:

  • Tiredness and a lack of energy
  • Shortness of breath
  • Pale skin
  • Heart palpitations[5]

How to keep Iron in the healthy range

Iron is essential for red blood cell health. A good source of iron is red meat and liver. It is recommended that red meat is consumed once per week to help keep iron levels within normal parameters. Women who are of menstruating age need to keep their iron intake increased particularly around the time of their periods. Individuals who follow a vegan or vegetarian diet will need to get their iron from plant-based sources.

Good food sources of iron are:

  • red meat
  • liver
  • green leafy vegetables e.g. spinach
  • dried fruit
  • pulses
  • nuts
  • seeds

The absorption of iron from plant-based sources is better when vitamin C is present. [6] For example, fortified breakfast cereals paired with a glass of orange juice. Tea can affect the absorption of iron, so you should refrain from drinking tea with your meals and switch to drinking it between meals. [7]

It is possible to get all the iron you need from a varied and balanced diet. Therefore, there should be no need to take iron supplements. However, a doctor may recommend supplements if your iron levels are considerably low.

Iron levels can be influenced by too much or too little exercise. Not having enough iron can affect your muscles ability to recover following exercise.

- Health scores calculated



[1] Abbaspour, N., Hurrell, R and Kelishadi, R. (2014). Review on Iron and its Importance for Human Health. Journal of Research in Medical Sciences: 19(2), pp 164-174.

[2] Lab Tests Online UK. (2019). Iron Tests. Available at:

[3] The Open University. (2017). Nutrition: Vitamins and Minerals.

[4] McDowell, L, A and Sticco, K, L. (2019). Iron Overload. In: StatPearls [Internet].

[5] NHS. (2018). Iron Deficiency Anaemia. Available at:

[6] 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.

[7] 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.

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This information has been medically reviewed by Dr Nicky Keay

Nicola has extensive clinical and research experience in the fields of endocrinology and sport and exercise medicine. Nicky is a member of the Royal College of Physicians, Honorary Fellow in the Department of Sport and Exercise Sciences at Durham University and former Research Fellow at St. Thomas' Hospital.

Dr Nicky Keay

Dr Nicky Keay

BA, MA (Cantab), MB, BChir, MRCP.