If my iodine is low, what’s the safest supplement dose and duration?

The short version: no retrieved trial gives a safe dose or duration for an iodine-deficient adult, and the one dose that appears in the records is a caution, not a recipe.

The records that actually tested iodine supplementation were mostly in pregnant women or deficient children, not in a general adult with low iodine. A 2026 meta-analysis found that 200–300 µg/day of potassium iodide lowered TSH and thyroglobulin in iodine-deficient pregnant women, but did not change free T3, free T4, or thyroid antibodies [3]. That is a lab-value benefit, not a proven clinical one. A Gambia trial found no difference in maternal thyroid function from prenatal iodine [4]. The one adult case report used 130 mg daily for three months and saw TSH fall [2]. That is a single person, no control, and iodine status was never measured before treatment. It is not a dose to copy.

The risk side is real. In a Spanish pregnancy study, high supplement intake was linked to thyroid dysfunction even in iodine-sufficient areas [5]. In North Indian pregnant women, higher urinary iodine tracked with thyroid autoantibodies [1]. In Chinese adults, both iodine deficiency and iodine excess were linked to autoimmune thyroid disease [6]. The pattern is a U-shaped curve, not "more is better."

What this retrieval cannot see: no trial compared a low-dose supplement against placebo in non-pregnant iodine-deficient adults and measured hard outcomes. That is the study that would settle dose and duration, and it is not here.

My call: if you are a non-pregnant adult with confirmed low iodine, food sources and iodized salt come first, and any supplement should be small and short, with TSH and free T4 checked before and after. Do not take the 130 mg dose from that case report. Confidence: low, because the adult trial data is thin and the dose question was never properly tested.