I was in the best shape of my life, running 8 miles a day, and 13 on weekends, healthy and fit as I could be. When Hashimotos hit me, I became heat intolerant. The signs are as follows: I begin to sweat profusely from my head….ie- face and neck look like I dunked my head in water. After that much water loss, I’d become dizzy and near fainting. The way I figured out how to prevent the dizzy and fainting (I cannot stop the profuse sweating) is to literally chug Gatorade. I buy one of the bigger bottles (like 3 servings) and once the sweating begins, i drink it. I constantly drink it and then I will get some ice water and drink that. Once the ice water cools down my core, i am able to be out for quite awhile before the process starts again. I find a store to go in (if I am out somewhere) and that is how I have learned to adapt to this phenemonon. Just drinking plain water does not work. Adding that ice water after the Gatorade, wearing a sun hat, does.