What are the side effects of sodium iodide I 131?

Sodium iodide I 131 may cause different side effects depending on why it is being used. Side effects after treatment of a hyperactive thyroid gland may resemble symptoms of an underactive thyroid and may include:
  • muscle aches
  • headaches
  • dry and puffy skin
  • weight gain
  • clumsiness
  • coldness
  • changes in menstrual cycles
  • temporary thinning of hair
Unusual side effects may include:
  • fast heartbeat
  • excessive sweating
  • heart palpitations
  • irritability
  • fever
  • unusual tiredness
Possible side effects of sodium iodide I 131 in the treatment of thyroid cancer include:
  • lower back or side pain
  • fever or chills
  • painful or difficult urination
  • bloody urine and stools
  • black, tar-like stools
Seek immediate medical care if you experience any of these symptoms, of if you have itching, an irregular heartbeat, vomiting or hives. 

Call 911 for signs of an allergic reaction including difficulty breathing, swelling of the mouth, lips, throat or tongue.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.