Dr. Clark is one of the few that advise internal use of Lugol's Solution and I have done this and had no ill effects, but I still caution that iodine is a strong poison.
One old timer test;
Take homemade Lugol's Solution and a pie plate. Put the iodine on the plate and run your feet in the iodine until the bottoms are all black. 24 hours later if all the iodine is gone, repeat. If iodine shows, your OK.
This is about 100 years old and people still do it and I have not heard any bad results. I make it, but do not promote it.