I have just been taking Lugol's, but I initially felt more cold and tired for many weeks. It's been off and on since then, but I've read a lot of people get more symptoms of hypothyroid for awhile before it starts getting better. I think dr. Brownstein even mentions that. I am not sure why, maybe the thyroid adjusting. I will also say that I was only on 25mg for about 4 months and just recently increased the dose to 50. I tried to go up to 100 very quickly after having some detox at 50mg, but that seemed to set of a cascade of detox stuff I'm apparently not clean enough (elimination channels) to dump without suffering more than what I can handle and still work. I'm planning to focus on some cleansing now and building circulation and oxygenation, and then try again to increase the dose later. It's been a lot of 2 steps forward, one step back for me with a lot of my health protocols, and so far Iodine is no different. I'm overall better than when I started experimenting, but it's not been straight uphill progress. Setbacks along the way, but many were self induced if I'm honest.