How do you know how much iodide I should be taking?

It depends on your thyroid markers and how much iodine shows up in your hair. If your iodine levels are adequate and your thyroid markers suggest you don't have subclinical hypothyroidism, then you can simply take 150 mcg each day as a maintenance dosage. If you do have subclinical hypothyroidism, you'll want to take 500 mcg per day at least. Sometimes even more. But I need to see blood work and your hair test to make that decision. Because it depends on your TSH, T4 levels and iodine levels.