It depends on how bad your LACK of Iodine is. For someone that is neither hypo or hyper and has no nodules jumping right in may be OK.
For me: I had numerous nodule on my thyroid. Even small amounts of Iodine made me feel like I was dying. I slowly worked up to 50 MG over 9 months.
6 MG for 4 weeks then 12 MG for 4 weeks and so forth. The first dose of 1/2 of a 12.5 Iodoral incapacitated me for 3 days.
Grizz is correct about there is no such thing as an overdose except if you have already had such low Idodine that your body chemistry is damaged.
I have read about humanitarian campaigns in Africa that give children 10 Grams once a year.
I would suggest just keep raising the dosage until you feel ill. If you feel ill stay at that dosage until you feel OK.