You don’t have to guess at iodine status — there are ways to measure it, each with strengths and limits.
A single random urine sample. Useful for population snapshots (WHO calls under 100 mcg/L deficient), but it swings with your last meal and doesn’t reflect what your tissues are holding.
Collecting all urine for a day is more accurate than a spot test, but still mostly reflects recent intake rather than tissue saturation.
You take a 50 mg dose of iodine, then collect all urine for 24 hours and measure how much you excrete. The logic: saturated tissues spill the excess, while depleted tissues hold onto it.
It’s the best pre-treatment assessment and can be repeated after 3–6 months to confirm repletion.
TSH, free T4, free T3, and thyroid antibodies (TPO-Ab, Tg-Ab) round out the picture. Note that a “normal” TSH doesn’t guarantee adequate iodine — the thyroid can adapt and keep TSH in range while tissues remain under-supplied.
Compiled by Dr. Jason Dean from open scientific literature and the reference above. Educational only — not medical advice, and not evaluated by the FDA. Consult a qualified healthcare provider before changing your supplement, diet, or health routine.
