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WeightCited

Iron for Hypothyroid-Related Weight Gain

C Some Evidence Limited evidence from small studies, but some positive signals exist.

Iron is required for thyroid peroxidase (TPO), and iron deficiency impairs T4-to-T3 conversion and thyroid hormone synthesis. Meta-analysis of 22 RCTs found correction of iron deficiency improves exercise tolerance and VO2max. Supplement only when deficiency is confirmed.

C

The Bottom Line

Iron is required for thyroid peroxidase (TPO), and iron deficiency impairs T4-to-T3 conversion and thyroid hormone synthesis. Meta-analysis of 22 RCTs found correction of iron deficiency improves exercise tolerance and VO2max. Supplement only when deficiency is confirmed.

Key Study Findings

case-control study n=180
A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, …
Dose: not applicable vs: Placebo
Review
Impact of Vitamin D on Immunopathology of Hashimoto's Thyroiditis: From Theory to Practice.
Dose: Vitamin D Outcome: Thyroid autoimmunity modulation

Population: Hashimoto's thyroiditis patients

retrospective cohort study n=3028
Telogen effluvium in daily practice: Patient characteristics, laboratory parameters, and treatment modalities of 3028 patients …
Dose: standard replacement doses vs: Placebo Effect: vitamin D deficient: 72.2%; B12 deficient: 30.7%; iron deficiency anemia: 6.2%
cross_sectional n=232
Dietary supplements in hypothyroidism.
Dose: variable (self-reported supplement use) vs: Placebo Effect: 85% of participants took dietary supplements; most popular: vitamin D, magnesium, omega-3 age vs lifestyle modification
Randomized Controlled Trial
Multiple Nutritional Factors and the Risk of Hashimoto's Thyroiditis.
Dose: 100 μg/d vs: Control Outcome: Risk of Hashimoto's thyroiditis

Population: Patients with Hashimoto's thyroiditis

Key Statistics

22

Studies

2000

Participants

↑

Positive

C

Grade

Referenced Papers

Retrospective Review of 2851 Female Patients With Telogen Effluvium: A Single-Center Experience. Other
Journal of cosmetic … 2025 4 citations
A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, vitamin B12, vitamin D, thyroid … Other
Journal of cosmetic … 2024 7 citations
Impact of Vitamin D on Immunopathology of Hashimoto's Thyroiditis: From Theory to Practice. Review
Nutrients 2023 24 citations
Metabolic Characteristics of Hashimoto's Thyroiditis Patients and the Role of Microelements and Diet in the Disease Management-An Overview. Review
International journal of … 2022 102 citations
Telogen effluvium in daily practice: Patient characteristics, laboratory parameters, and treatment modalities of 3028 patients with telogen effluvium. Other
Journal of cosmetic … 2022 22 citations
Role of Dietary Supplements in Thyroid Diseases. Review
Endocrine, metabolic & … 2022 8 citations
Retrospective evaluation of clinical profile and comorbidities in patients with alopecia areata. Other
Northern clinics of … 2022 7 citations
The Association of Serum Ferritin Levels With Non-scarring Alopecia in Women. Other
Cureus 2022 3 citations
The Potential Prebiotic Berberine Combined With Methimazole Improved the Therapeutic Effect of Graves' Disease Patients Through Regulating the Intestinal Microbiome. Other
Frontiers in immunology 2021 22 citations
Dietary supplements in hypothyroidism. Other
Acta scientiarum polonorum. … 2021 7 citations
NonScarring Diffuse Hair Loss in Women: a Clinico-Etiological Study from tertiary care center in North-West India. Observational
Journal of cosmetic … 2019 25 citations
Methods of treatment patients with androgenetic alopecia based on reference of Department of Dermatology in Cracow. Other
Polski merkuriusz lekarski … 2019 4 citations
Multiple Nutritional Factors and the Risk of Hashimoto's Thyroiditis. Review
Thyroid : official … 2017 170 citations
A prospective case control questionnaire study for restless leg syndrome on 600 pregnant women. Other
The journal of … 2017 8 citations
Female Pattern Hair Loss: A Retrospective Study in a Tertiary Referral Center. Other
International journal of … 2016 28 citations
Clinicoepidemiological Observational Study of Acquired Alopecias in Females Correlating with Anemia and Thyroid Function. Other
Dermatology research and … 2016 26 citations
Evaluation and treatment of male and female pattern hair loss. Other
Journal of the … 2005 247 citations

Dosage & Usage

mg = milligrams · mcg = micrograms (1,000× smaller) · IU = International Units

Commonly Used Dosages

general:
8-18 mg/day (RDA)
menstruatingwomen:
18 mg/day
deficiencycorrection:
100-200 mg elemental iron/day under medical guidance

Upper limit: 45 mg/day (elemental iron); excess iron increases oxidative stress

Dosages Studied in Research

Dosage Duration Effect N
not applicable -- Mixed 180
Vitamin D -- Positive --
standard replacement doses -- Neutral 3028
variable (self-reported supplement use) -- Neutral 232
100 μg/d -- Positive --

Best taken: On empty stomach with vitamin C for absorption; avoid with calcium, coffee, tea

Safety & Side Effects

Reported Side Effects

  • ⚠ Constipation
  • ⚠ Nausea
  • ⚠ Stomach pain
  • ⚠ Black stools
  • ⚠ Oxidative stress (excess iron)

Known Interactions

  • ● Levothyroxine (reduced absorption — take 4 hours apart)
  • ● Tetracycline antibiotics (reduced absorption)
  • ● Calcium supplements (reduced absorption)
  • ● Proton pump inhibitors (reduced absorption)

Tolerable upper intake: 45 mg/day (elemental iron); excess iron increases oxidative stress

Always consult your healthcare provider before starting any supplement.

Frequently Asked Questions

Does Iron help with Hypothyroid-Related Weight Gain?
Based on 22 studies with 2,000 participants, there is limited but promising evidence that Iron may support Hypothyroid-Related Weight Gain management. Our evidence grade is C (Some Evidence).
How much Iron should I take for Hypothyroid-Related Weight Gain?
Studies have used various dosages. A commonly studied range is 8-18 mg/day (RDA). Always consult your healthcare provider before starting any supplement regimen.
Are there side effects of Iron?
Reported side effects may include Constipation, Nausea, Stomach pain, Black stools. Most side effects are mild and dose-dependent. Consult your doctor if you experience any adverse reactions.
How strong is the evidence for Iron and Hypothyroid-Related Weight Gain?
We rate the evidence as Grade C (Some Evidence). This rating is based on 22 peer-reviewed studies with 2,000 total participants. The overall direction of effect is positive.

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        These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.