Summary: It appears to be important to know if your thyroid is over or underactive before increasing iodine or iodine-containing herbs or supplements, such as kelp, bladderwrack and bugleweed.

Wikipedia: "Iodine deficiency may cause depression, brain fog, extreme fatigue, goiter, mental slowing, weight gain, and low basal body temperatures. It is reported that mental retardation can improve with iodine treatment. The same sympomes or worse can be present in too much iodine." (1)

Wikipedia: Potassium iodide is a white crystalline salt with chemical formula KI, used in photography and radiation treatment. It finds widespread application as an iodide source because it is less hygroscopic than sodium iodide, making it easier to work with. KI can turn yellow upon heating in air or upon standing in moist air for long periods, because of oxidation of the iodide to iodine." (2)

" Normal Thyroid Stimnulating Hormone (TSH) range for thyroid used to be .5 to 5.0 and is now considered to be .3 to 3.0 on the TSH blood test. A test below the range ment your thyroid was hyperthyroid/overactive and above is hpothyroid/underactive.  What this means for iodine is that those with overactive thyroid may be harmed by increasing iodine health suppliments." (3)

"It is reported that water treatments with fluorine, chlorine, and bromine create an iodine deficiency in humans." (4)

Lugol's solution "is an internal iodine solution designed to eliminate Candida and possibly viruses and other microbes from the bloodstream. Obtain 100ml of Lugol's solution, also labelled Aqueous Iodine Oral Solution B.P., from a chemist. Take a test drop in liquid other then just water to make it taste less strong. If this does not cause an allergic reaction, continue to take 4 x 6 drops daily in liquid or mixed with food, but not together with vitamins A, C, E, grape seed extract or cysteine. Iodine is an oxidant and it is best to reduce the intake of antioxidants while using it. Continue for 3 weeks, but interrupt if you develop a serious reaction. Do not take the iodine for more than 3 weeks as that interferes with thyroid activity. If necessary, repeat the course after several months. You may make Lugol's solution yourself by dissolving 44 g or 1.5 ounces of iodine and 88 g or 3 ounces of potassium iodide in one quart (liter) of water. First dissolve the potassium iodide in a pint of water, then add the iodine and fill up to one quart. Shake from time to time until dissolved after about a day. Instead of Lugol’s solution, also a saturated solution of potassium iodide (SSKI) appears to be effective if taken in similar amounts." (5)