Iron is a valuable micronutrient needed in the body for many activities – such as growth and development, immunity and most importantly, to make haemoglobin and myoglobin. Haemoglobin is a protein in the blood that binds to inhaled oxygen in the lungs and releases it as it travels throughout the body. Myoglobin is a protein that provides oxygen to muscles.
Iron is supplied to the body through the dietary intake of animal meat, vegetables, whole-grains, fortified foods and through supplementation and is the most common mineral for which people may be deficient.
Blood tests for iron
Any blood test ordered by a healthcare professional is used to help evaluate a patient’s health status. A blood test for iron may also be referred to as an iron panel, iron profile, iron status, iron indices or Fe studies. "Fe" is the chemical symbol for iron. This test is performed to evaluate the levels of iron in the body and is commonly ordered when investigating the cause of certain health symptoms or if anaemia or iron overload is suspected.
An iron study does not just inform on the level of iron circulating in the blood but may also reveal the condition of red blood cells and their ability to carry oxygen and how much iron is in storage.
Iron blood test results explained
An iron panel is designed to diagnose how iron is being metabolised. Tests performed will usually include fasting serum iron, percentage transferrin saturation, iron saturation and serum ferritin.
Serum iron. Measuring the amount of iron in the blood. When iron is low the body releases iron from storage.
Serum ferritin. Measuring the amount of iron stored in the body.
- In pregnancy a low ferritin level reading may indicate an iron deficiency at any stage of pregnancy, although in the final weeks of pregnancy, organic iron is transferred from mother to foetus.
Unsaturated iron-binding capacity (UIBC). Transferrin is the protein that carries the iron in the blood. This test measures the transferrin not attached to iron.
Total iron-binding capacity (TIBC). This test measures the amount of free TIBC. It equals UIBC plus the serum iron measurement. If the measure is high, it indicates iron levels are low because there is no iron to transport and vice versa, if levels are low, it indicates iron overload.
- Iron binding capacity decreases in liver diseases.
- levels may be low in multifactorial anaemias or anaemias associated with chronic inflammation
Transferrin saturation. This measures the percentage of transferrin which is attached to iron.
Some laboratories will test for UIBC, TIBC or transferrin.
What happens if anaemia is suspected?
If anaemia is suspected by a healthcare professional, a reticulocyte count may be included in the iron panel. Reticulocytes are immature red blood cells produced in the bone marrow. A reticulocyte count may indicate recent bone marrow activity and the adequacy of the production of red blood cells.
Bone marrow is continuously producing red blood cells to replace old cells, degraded cells, and those lost through bleeding. Old cells are around 120 days old. New blood cells are produced as stem cells and develop into reticulocytes. As they mature they are released from bone marrow into the blood. This balancing act of production and replacement may be disrupted by excess loss of red blood cells or a decrease in production from bone marrow.
What does this mean?
A decreased production of red blood cells may mean:
- decreasing number of reticulocytes due to the removal of old red blood cells but without replacement
- decreased numbers of red blood cells in circulation
- decreased amounts of haemoglobin (the protein which carries oxygen)
- decreased haematocrit (the number of cells as opposed to plasma in the blood)
The body will try to compensate by increasing the production rate of red blood cells in the bone marrow which increases the number of reticulocytes in the blood until balance is restored.
Bone marrow disorders, insufficient erythropoietin (a hormone produced by the kidney that stimulates red blood cell production), and nutrient deficiency (iron, vitamin B12 or folate) may cause a decrease in red blood cell production.
More on anaemia
The cause of anaemia may be determined through further blood tests.
Mean corpuscular volume (MCV)
The MCV measures the average size and volume of a red blood cell and is a laboratory test used to help determine the classification of anaemia, along with haemoglobin and haematocrit, as either:
Normocytic anaemia with MCV within the normal range. This is an anaemia in which the circulating red blood cells are the same size (normocytic) and have a normal red colour (normochromic) and is most often a consequence of some other diseases or disorders of the blood.
Microcytic anaemia with MCV below the normal range. This anaemia appears as small red blood cells and is most often caused by iron anaemia.
Macrocytic anaemia with MCV above the normal range. Divided into two forms:
- Megaloblastic (hypersegmented neutrophils) - caused by impaired DNA synthesis due to deficiencies of folate and/or vitamin B12 or
- Non-megaloblastic which occurs from multiple mechanisms
Haemoglobin carries oxygen to the cells in the body from the lungs. Low haemoglobin levels indicate anaemia.
Haematocrit (Packed cell volume; PCV; Hct) is the ratio of the volume of red blood cells to the total volume of blood.
- A lower-than-normal haematocrit may indicate anaemia
- Elevated haematocrit is due to an increase in the number of red blood cells or when the blood volume is reduced, as in dehydration.
Why might you need an iron blood test?
The most common reason a complete blood test is ordered is to check for iron anaemia, iron overload (hemochromatosis) or iron toxicity (iron poisoning). Simply - too much or too little iron. The symptoms of too little iron include:
- Tiredness/lethargy/weakness
- Dizziness
- Headache
- Tachycardia (fast heartbeat)
- Pale skin, the conjunctiva of the eye, mucosa of the mouth or the nail bed
What may cause iron deficiency?
Low iron levels will generally fall under one of the following causes - insufficient iron in the diet, issues with absorbency, or blood loss. Some examples include:
Insufficient iron in the diet
- Growth spurts in children
- Intense athletic training
- Vegan/vegetarian diet
Issues with absorbing iron
- Digestive disorders such as – such as Coeliac disease or ulcerative colitis
Bleeding disorders
- Menstrual bleeding
- Gastrointestinal bleeding
What happens if you have too much iron?
Too much iron is most commonly due to hereditary haemochromatosis, but may also occur in disorders that are dependent on blood transfusions. Symptoms include:
- Tiredness/weakness/fatigue
- Stomach pain
- Joint pain
Iron overload is a serious condition that may lead to a number of health complications affecting joints and organs such as the pancreas, liver and heart, where iron excess is stored. Skin colour may change to grey or bronze as the iron deposits into skin cells.
If you are concerned about your iron levels, please discuss this with your healthcare professional.
Related Reads:
References
- https://www.healthdirect.gov.au/iron-studies-blood-test
- https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
- https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/iron#stages-and-symptoms-of-iron-deficiency
- https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/haemochromatosis
- https://medlineplus.gov/lab-tests/reticulocyte-count/
- Annemarie Schop, Karlijn Stouten, Jürgen A Riedl, Ron J van Houten, Maarten J G Leening, Patrick J E Bindels, Mark-David Levin, The accuracy of mean corpuscular volume guided anaemia classification in primary care, Family Practice, Volume 38, Issue 6, December 2021, Pages 735–739, https://doi.org/10.1093/fampra/cmab034 https://academic.oup.com/fampra/article/38/6/735/6338483
- Faruqi, A. (2023, January 2). Iron binding capacity. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK559119/https://www.ncbi.nlm.nih.gov/books/NBK559119/
- Mean corpuscular volume. (2023, January 1). PubMed. https://pubmed.ncbi.nlm.nih.gov/31424859/
- Macrocytic anemia. (2023, January 1). PubMed. https://pubmed.ncbi.nlm.nih.gov/29083571/
- Yilmaz, G. (2023, February 24). Normochromic normocytic anemia. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK565880/
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