Supplements

ferritin causes fatigue

Leans support Supplements 🔬 Includes disconfirming

RefutedContestedStrong support

consensus score 0.27

📅 Last reviewed: 2026-07-15 ⓘ

Evidence ladder

How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."

Top evidence so far: All trials, pooled (Meta-analysis)

MechanismIn-vitroAnimalObservationalRCTMeta-analysis

How the studies fall

8 support 2 contradict 2 tested null 1 mixed · 13 sources, 10 independent groups

What the evidence shows

Iron deficiency (low ferritin, even without anemia) causes fatigue and cognitive symptoms; repleting iron improves them specifically in iron-deficient people.

Cochrane has no ruling yet see how our grade compares ▾

Cochrane review 2019 · limited Not directly comparable

TREATMENT question, not a causal one: it tests whether IV iron helps non-anaemic deficiency, not whether deficiency causes fatigue.

“Intravenous iron therapy for non-anaemic, iron-deficient adults (CD013084.pub2). '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.'”

Not directly comparable: their review asks a different question or reports an outcome we do not grade, so it neither corroborates nor contradicts this claim.

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The evidence (13)

Source	Grade	Stance	Quality	Finding
Lee A et al 2026 · study_type: observational	observational	supports	low	Case report: IDA pt, ferritin 1->52 ng/mL after IV iron; desiderosmia/pica-like symptom resolved fully alongside repletion.
Sultana N et al 2026 · study_type: RCT	RCT	supports	moderate	Double-blind placebo-RCT n=164, non-anemic (Hb>11) iron-deficient women: iron group had significant fatigue score decrease + ferritin/Hb rise vs placebo (p=0.05).
Fiani D, et al. 2025 · Neurosci Biobehav Rev	meta-analysis	supports	moderate	Iron supplementation improved fatigue d=0.34, cognition d=0.46, memory d=0.53; effects disappear when iron-deficient excluded (deficiency is the driver).
McErlean SME et al 2026 · study_type: observational	n-of-1	supports	low	Case report: collegiate athlete, non-anemic (Hb 14.1) ferritin 15ug/L, exercise intolerance; IV iron repletion improved symptoms + VO2peak 25.5→31.2 mL/kg/min at 5mo.
Kazak Salti A et al 2026 · study_type: observational	observational	supports	low	Hemodialysis n=78: low negative correlation between ferritin and Fatigue Severity Scale scores (direction not quantified with r/p in abstract).
Suyama A et al 2026 · study_type: observational	observational	tested-null	low	Long COVID n=811: low-IGF-I group had higher FAS fatigue (37.0 vs 34.0, p<0.05); IGF-I negatively correlated w/ ferritin (rho=-0.125, p<0.05) — ferritin itself only a weak secondary correlate.
Pervaz H et al 2026 · study_type: observational	observational	tested-null	low	Fibromyalgia n=241: ferritin lower in neuropathic-pain group (p=0.005) but multivariable regression showed only FIQR severity (not ferritin) independently predicted neuropathic pain.
Keller P, et al. 2020 · Sci Rep	RCT	contradicts	high	Single 800 mg IV ferric carboxymaltose vs placebo: fatigue 3.9 vs 4.0 (p=0.819, NULL) despite ferritin +114.
Harrabi MA et al 2026 · study_type: RCT	RCT	mixed	low	RCT n=38, young women w/ IDA (anemic), all received iron 494.5mg; +Tabata training group had greater fatigue reduction (MFI, p<0.001) vs untrained.
Harrabi MA et al 2026 · study_type: observational	observational	supports	moderate	Cross-sectional n=40 women w/IDA: postural-control (CoPv) correlated with Hb (p<0.01) and ferritin (p<0.05) and fatigue scores (p<0.05).
Sathiyamoorthi S et al 2026 · Research Square	observational	supports	low	Cross-sectional n=171 menstruating women; 26.9% had IDWA (ferritin<30, normal Hb); fatigue reported in 77.9% of all symptomatic women (no anemic/IDWA fatigue-rate split given).
Chakraborty R et al 2026 · study_type: RCT	RCT	supports	moderate	Pregnancy IDA RCT n=60: IV FCM vs oral ferrous sulfate; ferritin 73.1 vs 22.7 ng/mL, fatigue score improvement markedly greater with IV (p<0.001). Anemic population.
Waldvogel S, et al. 2012 · BMC Med	RCT	contradicts	high	Oral iron reduced fatigue vs placebo at ~3 wk.

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