Iron Deficiency: Symptoms, Causes and Treatment

01Iron and hemoglobin

Iron stores and hemoglobin

The NIH Office of Dietary Supplements (ODS) explains that the body uses iron to make hemoglobin, a protein in red blood cells that carries oxygen from the lungs to the rest of the body, and myoglobin, which supplies oxygen to muscles. Iron is also needed for growth, development and making some hormones.

The body keeps a reserve of iron in the muscles, liver, spleen and bone marrow. ODS notes that in the short term, getting too little iron does not cause obvious symptoms because the body uses these stores. Mayo Clinic explains that without enough iron the body cannot make enough hemoglobin, and the blood carries less oxygen.

02With or without anemia

Deficiency with or without anemia

Iron deficiency and iron deficiency anemia are related but not identical. ODS describes a sequence: first iron stores fall, and only when they become low does anemia set in, with red blood cells becoming smaller and containing less hemoglobin.

This means low iron stores can exist before anemia appears, and early on they may cause no clear symptoms. Mayo Clinic notes that iron deficiency anemia can at first be so mild that you do not notice it. Not every anemia is caused by low iron either: ODS explains that in anemia of chronic disease, linked to conditions such as rheumatoid arthritis, inflammatory bowel disease and some cancers, taking more iron usually does not help, and the main treatment is the underlying disease.

03Symptoms

Symptoms and why they are not diagnostic

As iron gets lower and anemia worsens, symptoms may include:

• extreme tiredness, weakness and lack of energy
• pale skin
• shortness of breath, chest pain or a fast heartbeat
• headache, dizziness or lightheadedness
• cold hands and feet
• a sore or irritated tongue and brittle nails
• restless legs syndrome
• cravings for non-food items such as ice, dirt or clay

ODS adds stomach upset and problems with concentration and memory. The NHLBI notes that people with mild or moderate iron deficiency anemia may have no symptoms. Tiredness and the other symptoms on this list have many possible causes, so they cannot confirm low iron on their own. Mayo Clinic advises not trying to diagnose or treat it yourself.

04Causes

Blood loss, absorption and dietary factors

Iron deficiency happens when the body does not get enough iron or loses too much. The sources describe three main groups of causes:

• Blood loss: heavy periods or bleeding during childbirth; slow bleeding in the digestive tract from ulcers, a hiatal hernia, colon polyps, inflammatory bowel disease or colorectal cancer; regular use of anti-inflammatory painkillers or aspirin; urinary tract bleeding; injuries and surgery.
• Poor absorption: celiac disease, Crohn’s disease, ulcerative colitis, Helicobacter pylori infection and surgery on the stomach or intestines, including weight loss surgery.
• Not enough iron in the diet or higher needs, as in pregnancy and growth spurts.

Groups at higher risk include people with heavy periods, pregnant people, infants and children, vegetarians and vegans who do not eat enough other iron-rich foods, frequent blood donors and people with kidney disease, cancer, heart failure or digestive conditions. The NHLBI also mentions endurance athletes.

05Tests

Interpreting tests with clinical context

The NHLBI explains that diagnosis is based on blood tests: a complete blood count (CBC), hemoglobin levels, blood iron levels and ferritin, which reflects the body’s iron stores. Your doctor may tell you that your blood iron is low, and whether or not you also have anemia.

Results are interpreted alongside your symptoms, history and other conditions. A single result outside the reference range is a starting point for discussion, not a diagnosis by itself, and reference ranges vary between laboratories and groups of people. Because inflammation and chronic disease can also affect iron, the doctor considers the whole picture before deciding on treatment.

06Underlying cause

Investigating the underlying cause

Mayo Clinic stresses that a health care professional needs to look for the cause of iron deficiency anemia. Treating the low iron without finding out why it happened can delay the diagnosis of conditions such as internal bleeding, celiac disease or other digestive diseases.

Depending on your age, sex, symptoms and history, investigation may focus on menstrual blood loss, digestive symptoms, medicines that can cause bleeding, diet or absorption problems. The NHLBI notes that iron deficiency anemia may be preventable if the causes of blood loss or poor absorption can be treated, and that surgery may sometimes be needed to stop internal bleeding.

07Food

Food sources and absorption

The sources list iron-rich foods such as lean red meat, poultry and seafood, beans, lentils, peas and other legumes, tofu, eggs, dark green leafy vegetables such as spinach, nuts, dried fruits such as raisins and apricots, and breads, cereals and pastas with added iron.

Iron in food comes in two forms. ODS explains that heme iron, found in meat, poultry and seafood, is absorbed better than nonheme iron from plant foods, and that vegetarians may need almost twice as much iron as recommended for others. Eating plant sources of iron together with vitamin C-rich foods such as citrus fruits, strawberries, peppers, tomatoes and broccoli improves absorption, while the NHLBI notes that some drinks such as black tea can reduce it. Our guide on iron-rich foods for vegetarians has practical ideas. In our nutrition practice in Bilbao we offer dietary support for adults alongside medical care; we do not replace medical investigation or prescribe iron (consultations are in Spanish).

08Treatment

Oral or intravenous treatment when indicated

Diet helps prevent iron deficiency and supports treatment, but once deficiency or anemia has developed, food alone is often not enough. The NHLBI describes oral iron supplements as the most common treatment, noting that it often takes three to six months to restore iron levels.

Intravenous iron, given through a vein, can restore levels in one or a few sessions and is more often used in people with severe anemia or long-term conditions. Blood transfusions may be used for serious anemia, and people with kidney disease may need medicines that help the bone marrow make red blood cells. The type, dose and duration of treatment are decided by your doctor.

09Sources

Where the sources differ

Mayo Clinic, the NHLBI and ODS agree on the main points, but they approach the topic differently:

• Focus. Mayo Clinic and the NHLBI describe iron deficiency anemia, while ODS explains iron as a nutrient and describes how stores fall before anemia appears.
• Other conditions. The NHLBI lists kidney disease and chronic inflammatory conditions among causes, while ODS explains that anemia of chronic disease usually does not improve with extra iron. Not every anemia is treated with iron.
• Daily amounts. ODS gives recommended daily intakes and upper limits for healthy people. These are not treatment doses: a doctor may prescribe more than the upper limit for a time to treat deficiency.
• Side effects and safety. The NHLBI lists metallic taste, nausea, constipation, diarrhea and stomach upset with oral iron. ODS warns that iron can interact with some thyroid and Parkinson’s medicines, stomach acid reducers and calcium, that people with hemochromatosis should avoid iron supplements, and that accidental iron overdose is a leading cause of fatal poisoning in children under 6, so supplements must be kept out of their reach.

10Summary

In summary

Iron deficiency develops when the body loses more iron than it takes in or cannot absorb enough. Stores fall first, and anemia follows, with tiredness, weakness, pale skin and shortness of breath. Blood tests including hemoglobin and ferritin confirm it, and finding the cause, such as blood loss or poor absorption, is as important as correcting the iron.

Iron-rich foods and vitamin C help, but treatment usually involves supplements prescribed by a doctor, and sometimes intravenous iron. Keep a simple record of your test results, possible blood loss, the medicines and supplements you take and how you feel, and review it with your doctor at follow-up. Talk to a professional before taking iron, and keep supplements away from children.