Iron deficiency symptoms

What symptoms does iron deficiency cause?

The NIH lists, among the functional losses associated with iron deficiency anemia, digestive complaints, weakness, fatigue, difficulty concentrating, and impairment of cognitive function, immunity, exercise and work performance, and body temperature regulation. In infants and children, untreated iron deficiency anemia can cause psychomotor and cognitive problems and resulting learning difficulties. ^[1]

The NIH also draws attention to an important limitation: people with iron deficiency often have other nutrient deficiencies too, which can cause other types of anemia or affect the severity of the anemia. A symptom therefore cannot be assumed to result from iron alone. ^[1]

The findings in the table are compiled from the clinical assessment section of the 2021 BSG guideline and from the NIH. The guideline states that these findings are seen “from time to time”; that is, in most people none may be obvious. ^[2]

What is iron deficiency without anemia?

Iron deficiency does not develop in a single step. In the first stage described by the NIH, only the stores decrease and serum ferritin falls. In the second stage (iron-deficient erythropoiesis), the stores are exhausted and the iron going to blood production and transferrin saturation decrease, but hemoglobin is usually in the normal range. The third stage is iron deficiency anemia, in which hemoglobin and hematocrit fall. ^[1]

For this reason, the inference “my hemoglobin is normal, my iron is adequate” is not always correct. Although hemoglobin and hematocrit are the most commonly used tests for screening iron deficiency, the NIH states that neither is sensitive or specific for iron deficiency. ^[1] The test that best shows the state of the stores is ferritin; details are on the ferritin page.

Does iron deficiency cause fatigue?

Fatigue is a known finding in anemia. The more disputed question is whether fatigue improves with iron in people who are not anemic but have low ferritin.

In France, Vaucher and colleagues randomized 198 menstruating women aged 18–53, recruited from the practices of 44 primary care physicians, who had unexplained fatigue, ferritin below 50 µg/L and hemoglobin above 12.0 g/dL, in a placebo-controlled, observer-blinded trial. For 12 weeks the women received oral ferrous sulfate (102 women) or placebo (96 women). The fatigue score fell by 47.7% in the iron group and 28.8% in the placebo group (difference −18.9 percentage points; 95% confidence interval −34.5 to −3.2). No significant difference was found in quality of life, depression and anxiety scores. Hemoglobin and ferritin rose in the iron group compared with placebo. The daily iron amount used in the study (80 mg elemental iron) is above the 45 mg upper limit reported by the NIH for healthy adults and is not a usage recommendation. ^[3]

The systematic review by Houston and colleagues covered 18 randomized trials (1,170 people) in non-anemic, iron-deficient adults. Iron reduced self-reported fatigue (standardized mean difference −0.38; 4 trials, 714 people); however, there was no difference in objective measures of physical capacity such as maximal oxygen consumption (9 trials, 235 people) and timed exercise tests. ^[4]

Read together, the two results indicate that in fatigued people with low ferritin, iron is associated with a moderate reduction in subjective fatigue; however, this does not show that every fatigue is caused by iron deficiency or that iron will relieve fatigue in a person with normal ferritin.

Is hair loss due to iron deficiency?

The review by Almohanna and colleagues reports that iron deficiency is common in women with hair loss, but that the relationship between low ferritin and hair loss has been debated for years. In a controlled study of 381 women cited in the review, iron deficiency was common in women but was not more frequent in those with female-pattern hair loss or chronic telogen effluvium than in the control group; the method of that study was later criticized. ^[6]

The review states that evidence is insufficient for an effect of iron replacement on the outcome of telogen shedding, with some benefits seen in only a few controlled studies. It also reports, however, that most authors support correcting the deficiency in people with hair loss in whom iron deficiency or low ferritin is found, and that there is no consensus on a “normal ferritin” level. ^[6] That is, hair loss can be a reason for testing iron; there is no evidence that iron stops hair loss in a person with normal ferritin.

Why do restless legs and ice craving matter?

According to the AASM, the cause of restless legs syndrome (RLS) is not fully understood; iron deficiency in the brain and genetic factors are thought to play a role. The 2025 guideline of the American Academy of Sleep Medicine (AASM) states, as a good practice statement, that ferritin and transferrin saturation should be tested routinely in all patients with clinically significant RLS. According to the guideline, testing should preferably be done in the morning and after avoiding iron-containing supplements and foods for at least 24 hours beforehand. ^[5]

Based on untested consensus opinion, the same guideline reports that in adults with RLS, oral or intravenous iron may be considered if ferritin is 75 ng/mL or below or transferrin saturation is below 20%, and intravenous iron only if ferritin is 75–100 ng/mL, and it stresses that these thresholds differ from those used for the general population. ^[5] These thresholds are specific to RLS treatment; they are not the answer to the general question of what ferritin level is normal.

The craving to eat non-food substances such as ice, soil or starch is called pica. The BSG lists craving for ice (pagophagia) among the findings more specific to iron deficiency and also lists pica in its table of causes of iron deficiency anemia. ^[2]

What causes iron deficiency?

Iron deficiency is not the name of a disease but a finding; its cause is investigated separately. The causes table of the BSG guideline includes the following headings: ^[2]

• Blood loss: Menstrual bleeding, bleeding from the digestive tract (ulcers, inflammatory bowel disease, polyps and tumors, vascular anomalies), from the urinary tract, and recurrent nosebleeds. Long-term use of pain relievers (NSAIDs) and blood donation are also listed.
• Malabsorption: Celiac disease, Crohn’s disease, reduced stomach acid, atrophic gastritis, Helicobacter pylori infection, stomach surgery or gastric bypass, PPI use.
• Low intake and foods that reduce absorption: Tea, coffee, calcium, flavonoids, oxalate and phytate; many antacids.
• Increased need: Pregnancy and growth periods; the NIH lists infants, young children, pregnant women and women with heavy menstrual bleeding among the main risk groups. ^[1]

According to the BSG, the most common cause in premenopausal women is menstrual bleeding; in men and postmenopausal women, iron deficiency anemia is often due to chronic blood loss from the digestive tract. About one third of these people have an underlying disease. ^[2]

Who is considered for testing?

Because the symptoms are not specific, the decision to test is made by considering symptoms, risk status and history together. Evaluation comes into consideration in people with one of the symptoms above who also carry a risk such as heavy menstrual bleeding, pregnancy, frequent blood donation, celiac disease, bariatric surgery or a predominantly plant-based diet. The NIH reports that iron deficiency develops in 25–35% of frequent blood donors. ^[1]

In adults with confirmed iron deficiency anemia, the BSG recommends that the initial investigation include urinalysis, celiac screening and, in appropriate cases, endoscopic examination of the upper and lower digestive tract. The guideline states that urgent evaluation of the digestive tract should be considered in new iron deficiency anemia without a clear explanation, because digestive tract cancers can present in this way without symptoms. ^[2]

What do data from Türkiye show?

A 2020 report by Ministry of Health experts cites 2010 data from the Türkiye Nutrition and Health Survey (TBSA): in women, iron deficiency as defined in the report was most common in the 31–50 age group (13.8%), the 19–30 group (12.4%) and the 12–18 group (10.1%); low serum ferritin was most common in women aged 31–50 (47.5%) and 19–30 (47.4%). ^[7]

The same report cites a 2011 Gazi University study in which hemoglobin was below 12 g/dL in 24.9% of mothers of children aged 6–17 months, low ferritin was found in 43.7% of the mothers and iron deficiency anemia in 6.9%. These data indicate that low ferritin in Türkiye may be much more common than anemia; however, thresholds and samples differ between studies, and the figures cannot be read as a single national prevalence rate. ^[7]

This page does not make a diagnosis or recommend personal doses. Symptoms, risk status and test results are evaluated together by a physician; deficiency needs to be confirmed before deciding to use iron.