Merck Manual

Please confirm that you are a health care professional

honeypot link

Iron Deficiency


Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last full review/revision May 2020| Content last modified May 2020
Click here for Patient Education

Iron (Fe) is a component of hemoglobin, myoglobin, and many enzymes in the body. Heme iron, contained mainly in animal products, is absorbed much better than nonheme iron (eg, in plants and grains), which accounts for > 85% of iron in the average diet. However, absorption of nonheme iron is increased when it is consumed with animal protein and vitamin C.

Iron deficiency is one of the most common mineral deficiencies in the world. It may result from the following:

Chronic bleeding due to colon cancer is a serious cause in middle-aged people and the elderly.

Diagnosis of iron deficiency involves complete blood count, serum ferritin and iron levels, and possibly measurement of transferrin saturation (iron-binding capacity). In deficiency states, iron and ferritin levels tend to be low, and iron-binding capacity tends to be high.

Rarely, when the diagnosis of iron deficiency remains uncertain, examination of bone marrow for iron may be necessary.

Treatment of iron deficiency involves correcting the cause if possible (eg, treatment of a bleeding intestinal tumor). All people with moderate or severe iron deficiency and some people with mild deficiency require iron supplementation.


  • 1. Coates A, Mountjoy M, Burr J: Incidence of iron deficiency and iron deficient anemia in elite runners and triathletes. Clin J Sport Med 1-6, 2016. doi: 10.1097/JSM.0000000000000390.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read
Test your knowledge
Folate Deficiency
Folates are involved in red blood cell maturation and synthesis of purines and pyrimidines. Folate is plentiful in fruits, organ meats (eg, liver), and which of the following food sources?  
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest