But you don't know if you have pre-existing thyroid issues. Prolonged use should include monitoring thyroid function.

see https://www.cdc.gov/healthywater/drinking/travel/backcountry...

Water that has been disinfected with iodine is NOT recommended for pregnant women, people with thyroid problems, those with known hypersensitivity to iodine, or continuous use for more than a few weeks at a time.