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I-131 scan dose

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  • I-131 scan dose

    I had a whole body scan with I-131 to check for recurrent thyroid cancer on 10/21/11. I weaned my 18 month old daughter before the scan. She was only nursing once a day for a short period of time before weaning. She did not want to wean and is indicating that she would still like to nurse. I know that I haven't completely dried up yet. I'm not sure how much the scan dose was, but I asked the nuclear medicine tech and he said that the I-131 should be out of my system in two weeks. Is this the case? I don't want to hurt my daughter, but if she wants to nurse I have no problem allowing her to do so, either.

  • #2

    I-131 has a radioactive half-life of 8 days. After 40 days, 98% is decayed away. It is hard to advise you with so little data, such as what was the dose in millicuries, do you have thyroid gland, etc.

    If you have not gland, then 2 weeks is probably OK, as most of the I-131 would be cleared by the kidney and eliminated quickly.
    If you have a gland that is still present, OR functioning, then I'd wait at least 30-40 days.

    Tom Hale PH.D.


    • #3
      I had a 4 millicurie dose for a scan. I have been searching EVERYWHERE and have gotten conflicting information from every medical professional I've asked. Frustrating! When might it be safe to resume very minimal (1x/day or less) with a much older child (age 3)? If he weans, it's certainly not the end of the world, but I want it to be his choice and don't want to discontinue for no reason. Thanks in advance.


      • #4
        I am having a PET w/a tracer dose of I-131 for recurrent Thyroid cancer as well, I have no thyroid. I'm told I will have to completely wean my 7mo old who is exclusively breastfed on solids twice a day. I'm so bummed & not prepared. This will likely be a difficult situation as she will not take a bottle & despises formula. I can't delay it as I have had my first thyrogen injection today & my PET is scheduled for Wednesday. Is this correct?


        • #5

          It's hard to advise you as I don't know the dose of I-131 your received. With no thyroid, it clears the body rapidly. With a thyroid, it hangs around for weeks and is very hazardous to your infant.

          In your situation, with no thyroid, you could probably return to breastfeeding by maybe 2-3 weeks. This also depends on the DOSE you received ? The data is not really clear here. In your situation with a 7 month old, I'm not sure it would be worth the risk to the infant. I'd suggest you don't sleep or stay within 6 feet of the infant for very long for 6 nights at least. Check page 1182 in my 2012 edition of MMM.

          Tom Hale Ph.D.