Serum iodine level low to high in 3 months

Have started Nature-throid this year and am up to 2 grains/day. Started Iodoral on 9/22/13 @ 12.5 mg/day - serum Iodine level showed 48ug/L...ref interval 40-92.
Am taking vit c (2000mg/day), 200 mg selenium/day, atp cofactors once a day, along with several other supplements.
My last test at the end of December showed my Iodine to be high at 134. How can this be? Especially at a low dose for only 3 months? Any insight would be appreciated!