Can low iron cause anxiety and depression?

Low iron and anxiety turn up together, and the trials say iron itself helps anxiety only a little, and only if you are short of it. In a Taiwan cohort of 19,397 adults with iron deficiency anemia, a new anxiety disorder was 47 percent more likely than in matched controls, but that is claims data and cannot show cause. The randomized evidence on anxiety is a 2025 meta-analysis in 1408 non-anemic children, adolescents and menstruating adults. In its trials iron eased anxiety by a small margin (d = 0.34) and did not change depression, and the benefit disappeared once iron-deficient people were taken out.

Unsettled. Whether low iron causes anxiety is not settled. The link is consistent across adults, children and postpartum women, but all of it is observational, and depression or anxiety could change eating as easily as the reverse. The one pooled trial result for anxiety is small, has no published confidence interval in the abstract, and mixes randomized trials with before-and-after studies.

Myth. Iron is not a mood supplement for people with normal stores. In the 2025 meta-analysis the effect was absent once iron-deficient participants were excluded, and the same trials found no change in depression at all.

What the trials found

Anxiety, in people who were short of iron

The 2025 meta-analysis pooled 18 studies in 1408 people who were not anemic, 12 of them randomized trials. In the trials, iron improved anxiety with a standardized effect of 0.34 and fatigue by the same amount. Depression and attention did not change. Subgroup analyses held for iron-deficient groups, young people and menstruating adults, and the effect vanished when iron-deficient participants were excluded. The review's confidence interval for anxiety is not in the abstract and we could not reach the full text.

Depression around pregnancy, no

A 2023 meta-analysis of randomized diet trials in pregnant and postpartum people found that iron, zinc and magnesium together did not beat placebo for perinatal depression (SMD -0.42, 95% CI -1.05 to 0.21). Iron was pooled with the other two metals, so this is not a clean test of iron alone, and the authors note iron may help only where deficiency is confirmed.

Fatigue, which is where iron clearly works

Tiredness is easy to mistake for low mood, and it is the symptom with the firmer trial evidence. Six randomized trials in fatigued people with iron deficiency but no anemia found a pooled effect of 0.33 (95% CI 0.17 to 0.48). In three trials in anemic postpartum women, iron lowered fatigue scores by 1.85 points (95% CI -3.04 to -0.67), a heterogeneous result from few trials. A Cochrane review of 11 trials of intravenous iron in 1074 adults with iron deficiency but no anemia found the evidence too weak to show any benefit beyond a small, clinically insignificant rise in hemoglobin.

The observational picture

In the Taiwan adult cohort, depression was also more common with iron deficiency anemia (aHR 1.49, 95% CI 1.33 to 1.66). Among those adults, the ones given iron did not have significantly less anxiety (aHR 0.91, 95% CI 0.80 to 1.03). In 2957 Taiwanese children and adolescents with the same anemia, anxiety disorder was about twice as common as in matched controls (OR 2.17, 95% CI 1.49 to 3.16). Seven observational studies of postpartum women found depressive symptoms 1.66 times as likely with iron deficiency or anemia, with high heterogeneity. A 2026 meta-analysis of 16 observational studies found serum iron lower in major depressive disorder (SMD -0.36). Three observational studies linked the highest dietary iron intake to 43 percent lower odds of depression, and diet quality could explain that. In US teenagers from NHANES, anemia with iron deficiency went with more severe anxiety only in multiracial adolescents (d = 3.00), a finding in a small subgroup.

Who should be careful

The practical point from the trials is to know your iron status first, because the benefit lived only in people who were deficient. The cautions below come from trials and the NIH fact sheet.

Not for everyone. Oral iron upsets the gut. In a Cochrane review of menstruating women, daily iron doubled gastrointestinal side effects in five trials (RR 1.99, 95% CI 1.26 to 3.12, low-quality evidence). In postpartum women, intravenous iron caused far less constipation than oral iron (RR 0.12, moderate certainty). NIH sets the adult upper limit at 45 mg a day. Iron can make levothyroxine less effective, and labels advise a 4-hour gap. People with hereditary hemochromatosis build up iron and, untreated, show iron toxicity by their 30s. Keep iron pills away from children: US labels warn that accidental iron overdose is a leading cause of fatal poisoning in children under 6.

What expert bodies say

The NIH Office of Dietary Supplements lists gut disturbances, weakness, fatigue and difficulty concentrating as symptoms of iron deficiency anemia. Its fact sheet does not list anxiety. That reflects what the fact sheet covers and does not prove there is no link. We found no guideline that recommends iron as a treatment for anxiety or depression.

How we searched

What would change this answer

• A randomized trial of iron with anxiety disorder as the main outcome. We found none. The US registry holds one recruiting trial (NCT06425796) with mental health only as a secondary outcome.
• A systematic review restricted to anxiety, with the confidence interval reported. The current pooled effect comes from a review that also covers fatigue, memory and before-and-after studies.
• A trial of iron alone for depression around pregnancy, in women with confirmed deficiency. The existing pooled result lumps iron with zinc and magnesium.
• Trials in adults with iron deficiency anemia, where the observational link is strongest. The trial evidence so far is in people who were deficient but not anemic.

Sources

1. ev-irax-01 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs and pre-post studies · n = 18 studies (12 RCTs, six pre-post), 1408 participants
   In RCTs, supplementation improved symptoms of anxiety (d = 0.34), fatigue (d = 0.34), physical well-being (d = 0.42), cognitive intelligence (d = 0.46), and short-term memory (d = 0.53) but not attention or depression.
   
   Who: non-anemic children and adolescents (5-17 years) and menstruating adults; RCTs and pre-post studies of iron supplementation
   Effect: RCTs: anxiety d = 0.34, fatigue d = 0.34; no effect on depression or attention
   Certainty: Small standardized effect; CI not in abstract (no PMC copy). Iron-deficient but non-anemic samples.
   Neurosci Biobehav Rev, 2025 · checked 2026-10-07 · we read the abstract
2. ev-irax-02 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs and pre-post studies · n = subgroup analyses of the same meta-analysis
   Subgroup analyses confirmed consistent results for ID-only groups, youth, and menstruating adults, though supplementation effects were absent when excluding ID participants.
   
   Who: non-anemic children, adolescents and menstruating adults; subgroup analyses
   Effect: effects consistent in ID-only subgroups; absent when ID participants excluded
   Certainty: Subgroup finding; supports testing ferritin before supplementing.
   Neurosci Biobehav Rev, 2025 · checked 2026-10-07 · we read the abstract
3. ev-irax-03 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 36 studies included, 28 meta-analyzed
   Elemental metals (iron, zinc, and magnesium) were also not found to be superior to placebo (SMD: -0.42; 95% CI: -1.05 to 0.21), although vitamin D yielded a small to medium effect size improvement (SMD: -0.52; 95% CI: -0.84 to -0.20) in postpartum depression.
   
   Who: pregnant and/or postpartum persons in RCTs of dietary interventions for depression or anxiety
   Effect: elemental metals (iron, zinc, magnesium) vs placebo SMD -0.42 (95% CI -1.05 to 0.21)
   Certainty: Metals pooled together; authors note iron may help only with confirmed deficiency.
   Am J Clin Nutr, 2023 · checked 2026-10-07 · we read the abstract
4. ev-irax-04 · Meta-analysis or systematic review · meta-analysis of RCTs and cross-sectional studies · n = 6 RCTs
   In the meta-analysis of the six RCT, we identified a significant therapeutic effect of Fe in fatigue patients with IDNA (pooled effect size 0·33; 95 % CI 0·17, 0·48; I 2=0·0 %; P<0·0001).
   
   Who: fatigue patients with iron deficiency without anemia
   Effect: pooled effect size 0.33 (95% CI 0.17-0.48), I2 = 0%
   Certainty: Fatigue, not anxiety; the six cross-sectional studies showed no significant association.
   Br J Nutr, 2017 · checked 2026-10-07 · we read the abstract
5. ev-irax-05 · Observational data · meta-analysis of observational studies · n = 7 observational studies
   Seven observational studies with pooled dichotomous outcomes showed that iron deficient or anaemic women were 1.66 times more likely to experience symptoms of depression than non-anaemic or iron-replete women [RR = 1.66 (95% CI: 1.28; 2.16), I2 = 67.0%, P < 0.01].
   
   Who: postpartum women, iron deficient or anemic vs non-anemic or iron-replete
   Effect: RR 1.66 (95% CI 1.28-2.16), I2 = 67%
   Certainty: Observational, high heterogeneity; association, not cause.
   BMC Public Health, 2022 · checked 2026-10-07 · we read the abstract
6. ev-irax-06 · Meta-analysis or systematic review · meta-analysis of RCTs (subset of a systematic review) · n = 3 RCTs
   In three randomized controlled trials (RCTs), pooled continuous data showed statistically significant reduction in fatigue scores in women who received iron supplementation than the control group [MD: -1.85 (95% CI: -3.04; -0.67), I2 = 65.0%, p < 0.06].
   
   Who: anemic postpartum women, iron supplementation vs control
   Effect: fatigue MD -1.85 (95% CI -3.04 to -0.67), I2 = 65%
   Certainty: Three trials, heterogeneous; fatigue only.
   BMC Public Health, 2022 · checked 2026-10-07 · we read the abstract
7. ev-irax-07 · Observational data · retrospective cohort · n = 19,397 IDA patients and 38,794 controls
   Among the different types of psychiatric disorders, the IDA group was associated with significantly higher incidence and risks of anxiety disorders (aHR = 1.47, 95% CI = 1.33–1.63, p < 0.001)
   
   Who: adults 20 years or over with newly diagnosed IDA, Taiwan National Health Insurance Database 2000-2012, matched 1:2 by age and gender
   Effect: anxiety disorders aHR 1.47 (1.33-1.63); depression aHR 1.49 (1.33-1.66); in IDA patients iron supplementation vs none, anxiety aHR 0.91 (0.80-1.03), not significant
   Certainty: Claims data, diagnosis codes; within IDA, supplementation lowered overall psychiatric risk (aHR 0.85) but not anxiety specifically.
   BMC Psychiatry, 2020, Psychiatric disorders risk in patients with iron deficiency anemia and association with iron supplementation medications: a nationwide database analysis · checked 2026-10-07 · we read the fulltext
8. ev-irax-08 · Observational data · case-control · n = 2957 patients with IDA
   A total of 2957 patients with IDA, with an increased risk of unipolar depressive disorder (OR = 2.34, 95% CI = 1.58 ~ 3.46), bipolar disorder (OR = 5.78, 95% CI = 2.23 ~ 15.05), anxiety disorder (OR = 2.17, 95% CI = 1.49 ~ 3.16)
   
   Who: children and adolescents with IDA vs age- and gender-matched controls (1:4), Taiwan National Health Insurance Database 1996-2008
   Effect: anxiety disorder OR 2.17 (1.49-3.16); unipolar depression OR 2.34 (1.58-3.46)
   Certainty: Odds ratio, claims-based diagnoses; direction of causation unknown.
   BMC Psychiatry, 2013 · checked 2026-10-07 · we read the abstract
9. ev-irax-09 · Observational data · cross-sectional · n = 1990
   Moreover, ID with anemia was associated with more severe anxiety (d = 3.00, p = 0.0130) and worse mental well-being (d = 2.75, p = 0.0059) in multiracial adolescents.
   
   Who: US adolescents 12-17 years, NHANES, 85.7% female
   Effect: ID with anemia and anxiety severity d = 3.00 (p = 0.013) in multiracial adolescents only
   Certainty: Subgroup finding in a small subgroup; cross-sectional.
   Nutrients, 2024 · checked 2026-10-07 · we read the abstract
10. ev-irax-10 · Observational data · meta-analysis of observational studies · n = 16 observational studies
    iron (SMD = -0.36; 95 % CI: -0.52 to -0.20; I2=58.2 %) were lower in MDD patients
    
    Who: individuals with major depressive disorder vs healthy controls
    Effect: serum iron SMD -0.36 (95% CI -0.52 to -0.20), I2 = 58.2%
    Certainty: Case-control comparisons; depression could lower intake rather than the reverse.
    Rev Environ Health, 2026 · checked 2026-10-07 · we read the abstract
11. ev-irax-11 · Observational data · meta-analysis of observational studies · n = 3 studies
    The pooled RRs with 95% CIs of depression for the highest versus lowest dietary zinc and iron intake were 0.67 (95% CI: 0.58-0.76) and 0.57 (95% CI: 0.34-0.95), respectively.
    
    Who: observational studies of dietary iron intake and depression
    Effect: highest vs lowest dietary iron RR 0.57 (95% CI 0.34-0.95)
    Certainty: Only three studies; diet quality confounding likely.
    Psychiatry Res, 2017 · checked 2026-10-07 · we read the abstract
12. ev-irax-12 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 11 studies, 1074 participants
    Current evidence is insufficient to show benefit of intravenous iron preparations for the treatment of non-anaemic iron deficiency across a variety of patient populations, beyond stating that it may result in a small, clinically insignificant increase in haemoglobin concentration.
    
    Who: adults with non-anemic iron deficiency, intravenous iron vs placebo
    Effect: insufficient evidence of benefit; small, clinically insignificant rise in hemoglobin
    Certainty: Very low quality; mood outcomes not separately pooled.
    Cochrane Database Syst Rev, 2019 · checked 2026-10-07 · we read the abstract
13. ev-irax-13 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 5 studies, 521 women
    Five studies recruiting 521 women identified an increased prevalence of gastrointestinal side effects in women taking iron (RR 1.99, 95% CI 1.26 to 3.12, low quality evidence).
    
    Who: menstruating women, daily oral iron vs control
    Effect: GI side effects RR 1.99 (1.26-3.12), 5 studies, 521 women
    Certainty: GI effect low-quality evidence.
    Cochrane Database Syst Rev, 2016 · checked 2026-10-07 · we read the abstract
14. ev-irax-14 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 33 RCTs, 4558 women
    Oral iron probably increases the risk of constipation compared to intravenous iron (RR 0.12, 95% CI 0.06 to 0.21; P < 0.001; I² = 0%; 10 RCTs; 1798 women; moderate-certainty evidence).
    
    Who: women with postpartum hemoglobin 12 g/dL or less, treated within six weeks after childbirth
    Effect: constipation IV vs oral RR 0.12 (0.06-0.21), 10 RCTs, 1798 women; IV iron fatigue SMD -0.25 (-0.42 to -0.07)
    Certainty: Moderate certainty; IV iron hypersensitivity very uncertain.
    Cochrane Database Syst Rev, 2024 · checked 2026-10-07 · we read the abstract
15. ev-irax-15 · Position of an expert body · agency fact sheet · n = —
    People with iron deficiency anemia may experience gastrointestinal disturbances, weakness, fatigue, and difficulty concentrating.
    
    Who: General population, NIH Office of Dietary Supplements iron fact sheet
    Effect: symptom list: GI disturbances, weakness, fatigue, difficulty concentrating, impaired cognition
    Certainty: Agency summary; absence of anxiety reflects the fact sheet, not proof of no link.
    NIH Office of Dietary Supplements, Iron fact sheet for health professionals · checked 2026-10-07 · we read the section
16. ev-irax-16 · Position of an expert body · agency fact sheet · n = —
    The Tolerable Upper Intake Level for iron is 45 mg for adults, and it ranges from 40 mg to 45 mg for infants, children, and adolescents, depending on age.
    
    Who: General population, NIH Office of Dietary Supplements iron fact sheet
    Effect: UL 45 mg/day adults, 40-45 mg/day for infants, children and adolescents
    Certainty: Treatment doses above the UL are prescribed under medical supervision.
    NIH Office of Dietary Supplements, Iron fact sheet for health professionals · checked 2026-10-07 · we read the section
17. ev-irax-17 · Position of an expert body · agency fact sheet · n = —
    The labels for some of these products [107,108] warn that iron supplements can reduce the absorption of levothyroxine tablets and advise against administering levothyroxine within 4 hours of iron supplements.
    
    Who: General population, NIH Office of Dietary Supplements iron fact sheet
    Effect: separate levothyroxine and iron by 4 hours
    Certainty: Relevant because thyroid disease also causes anxiety and low mood.
    NIH Office of Dietary Supplements, Iron fact sheet for health professionals · checked 2026-10-07 · we read the section
18. ev-irax-18 · Position of an expert body · agency fact sheet · n = —
    WARNING: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6.
    
    Who: General population, NIH Office of Dietary Supplements iron fact sheet
    Effect: FDA label warning; keep out of reach of children
    Certainty: Regulatory warning quoted by NIH.
    NIH Office of Dietary Supplements, Iron fact sheet for health professionals · checked 2026-10-07 · we read the section
19. ev-irax-19 · Position of an expert body · agency fact sheet · n = —
    Without treatment by periodic chelation or phlebotomy, people with hereditary hemochromatosis typically develop signs of iron toxicity by their 30s [3].
    
    Who: General population, NIH Office of Dietary Supplements iron fact sheet
    Effect: untreated: signs of iron toxicity by their 30s
    Certainty: Agency summary; the advice to test first is the editorial inference.
    NIH Office of Dietary Supplements, Iron fact sheet for health professionals · checked 2026-10-07 · we read the section