Iodine absorption / metabolism in the body

Consumed Iodide ions (I^-) are easily absorbed through the walls of the digestive tract in the stomach and small intestine duodenum and on into the blood and plasma.

Supplemental elemental iodine (I₂) also finds its way into the blood and plasma (in rat studies).    That is, provided the oral  dosages are high enough. This is inconsistent with the commonly held view that iodine (I₂) is reduced to iodide (I^-) before it is absorbed systemically from the gastrointestinal tract.

Thrall KD, Bull RJ, Differences in the distribution of iodine and iodide in the Sprague-Dawley rat. Fundam Appl Toxicol. 1990 Jul;15(1):75-81 PubMed

Thrall KD, Bull RJ, Sauer RL,  Distribution of iodine into blood components of the Sprague-Dawley rat differs with the chemical form administered. J.Toxicology enviro.Hea;th, 1992 Nov. 37(3) 443-9  PubMed

 Iodine is transported in the blood as  Iodide ions (I^-)  (its ionized form )

 Iodine is transported in serum proteins and lipids as elemental iodine (I₂ )

We do not conserve iodine long-term and so it must be obtained regularly via diet or supplementation.     With an iodine deficiency, the body conserves iodine for a while, but if the inadequacy continues, thyroid hormone is slowly depleted.