Tired of Being Tired: Iron Deficiency and Iron Deficiency Anemia

You get plenty of sleep. You eat a balanced diet. Yet, you still feel exhausted all the time.

You are not alone. Thirty-eight percent of the U.S. workforce reports feeling fatigued[1]. And general practitioners reported that 25 percent of their patients visited them complaining of fatigue with 25 percent of those who said it was their primary or secondary symptom.[2]   

If you or someone you know complains of fatigue, it may be due to an iron deficiency. Iron deficiency, with or without anemia, is one of the leading causes of fatigue and muscular weakness. [3] For women of childbearing age, studies have found that iron deficiency without anemia may be a risk factor for fatigue, tension, and anger.[4]

What does iron do? At the cellular level, iron is the primary component of hemoglobin (in the blood) and myoglobin (in the muscles). Iron bonds to oxygen molecules, and hemoglobin helps carry oxygen to cells for energy production, and carries away carbon dioxide. Repeating this oxygen pick-up and drop-off process, iron delivers about a quart of oxygen to your cells each minute. Myoglobin stores and releases oxygen for energy formation. Insufficient iron means insufficient oxygen for exerting energy.


Iron deficiency is a decrease of the total content of iron in the body, and it may result from either excessive iron loss or decreased iron absorption.[5] Diagnosing iron deficiency is not simple. Physicians may test for low serum ferritin (ferritin is a blood cell protein that contains iron[6] ) or low Transferrin Saturation percentage with an elevated Total Iron Binding Capacity (TIBC). Normal results[7]:

  • Ferritin: 12-300 ng/mL (nanograms per millilter) for men and 12-150 ng/mL for women
  • Iron: 60-170 micrograms per deciliter (mcg/dL)
  • Transferrin saturation: 20-50%
  • TIBC: 240-450 mcg/dL

A physician will typically use a combination of several tests and their results to determine whether an individual has iron deficiency.


Iron deficiency is the leading cause of anemia. Anemia is when the body does not have enough red blood cells to carry sufficient oxygen to your tissues and organs. The World Health Organization (WHO) defines anemia as a hemoglobin value <12.0 g/dL in women and <13.7 g/dL in men.[8]

Normal results for adults vary, but in general are:[9]

  • Male: 13.8 to 17.2 grams per deciliter (g/dL)
  • Female: 12.1 to 15.1 g/dL


Taking an oral iron supplement is front line therapy for treating iron deficiency, with or without anemia. Iron supplementation should be considered for women with unexplained fatigue[10]

Oral iron is not recommended for conditions such as gastric bypass, heavy uterine bleeding, inflammatory bowel disease, and hereditary hemorrhagic telangiectasia. For patients intolerant of or unresponsive to oral iron, intravenous administration is the preferred route.[11]

Most importantly, identify the cause of your iron deficiency or anemia. In the absence of a clear cause, a search for a source of bleeding is indicated. You and your physician should work together to identify the underlying cause and the long-term treatment.  


[1] Ricci, JA, Chee E, Lorandeau AL, and Berger J, “Fatigue in the U.S. workforce: prevalence and implications for lost productive work time, Journal of Occupational and Environmental Medicine, January 2007, pp 1-10.

[2]Cullen w, Kearney Y, and Bury G, “Prevalence of fatigue in general practice”, Irish Journal of Medical Science, Jan- Mar 2002

[3]Lasocki, S, Chadeau N, Papet T et al, “Prevalence of iron deficiency on ICU discharge and its relation with fatigue: a multicenter prospective study”, Critical Care, September 30, 2014

[4]Sawada t, Konomi A, and Yokoi K, “Iron deficiency without anemia is associated with anger and fatigue in young Japanese women”, Biological Trace Element Research, June 2014 pp 22 – 31

[5] Bermejo, F and Garcia-Lopez, Santiago, “A guide to diagnosis of iron deficiency and iron deficiency anemia in digestive diseases”, World Journal of Gastroenterology, October 7, 2009, pp 4,638-4,643

[6]Ferritin Test, < http://www.mayoclinic.org/tests-procedures/ferritin-test/basics/definition/prc-20014449 > accessed January 12, 2016

[7] Total Iron Binding Capacity, < https://www.nlm.nih.gov/medlineplus/ency/article/003490.htm > accessed January 12, 2016

[8] World Health Organization, “Iron Deficiency Anaemia, Assessment, Prevention and Control”, 2001, p 33

[9]Hemoglobin, U.S. National Library of Medicine Medline Plus < https://www.nlm.nih.gov/medlineplus/ency/article/003645.htm > , accessed January 13, 2016

[10]Vaucher, P, Druais, PL, Waldvogel S, and Favrat, B, “Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin; a randomized controlled trial”, Canadian Medical Association Journal, August 7, 2014, pp 1247 - 1254

[11]Auerbarch M, Adamson JW, “How We Diagnose and Treat Iron Deficiency Anemia”, American Journal of Hematology, September 26, 2015