All of the Iodine doctors and the Curezone Iodine Group recommend Lugols liquid or Iodoral capsules. This is because they both contain the recommended amount of both Iodine and iodide, both required by our body.
You must also take the recommended co-supplements, especially selenium. Selenium is required to be taken with iodine to prevent thyroid problems such as hashi & thyroid storms.
PS) Chart your body temp and as you are taking iodine, you will be scaling out of synthroid. Your thyroid needs iodine, to function properly, not synthroid.