I’ve never been tested — I chose to supplement without. But my official position is that anyone considering iodine supplementation should consult a healthcare practitioner knowledgeable about iodine for guidance, which will likely entail testing. The fact is many of us are heavily burdened with the halides you mention and are likely to experience some detoxification when we start taking iodine. I suspect, in fact, that I am still dealing with this some 18 months after I started. Bottom line is educate yourself and don’t imagine this will be a quick fix: undoing years of damage doesn’t happen overnight!