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WeightCited

Iron for Hypothyroid-Related Weight Gain

C

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.

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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 Statistics





            


    

        
22

        
Studies

    

    

        
2000

        
Participants

    

    

        
            
            ↑
            
        
        
Positive

    

    

        C

        
Grade

    




        


        
        

        
        
        

            

  
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
                

                
            

            

            

            
            

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

            
        

        

        
        
        

            

  
Safety & Side Effects





            

                
                

                    
Reported Side Effects

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

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

    

    




        

        

        
        
        

            

  
Related Evidence





            

                

                
                
                
            

        

        

    


    
    












    

        FDA Disclaimer:
        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.