Iodine is a trace mineral required for the production of thyroid hormones, which regulate metabolism, energy, growth, and development. Your body cannot make iodine on its own, so it must come from dietary sources such as seafood, dairy, eggs, and iodised salt. In Australia, mild to moderate iodine insufficiency is more common than many people realise, particularly among those on restrictive diets, those who avoid iodised salt, or those who eat little seafood.
Standard iodine tests, such as a spot urine sample, measure recent dietary intake. While useful for screening, they fluctuate with what you ate in the past day or two and do not reliably reflect whether your body's overall stores are adequate. The iodine loading test takes a different approach. You ingest a measured dose of iodine, then collect all urine over the following 24 hours. The percentage of iodine your body excretes versus retains indicates how saturated your tissues are. If stores are adequate, you excrete most of the dose. If stores are depleted, your body holds onto a larger proportion.
This challenge method provides a more detailed assessment of whole-body iodine status than spot testing alone. It is particularly relevant for people with thyroid symptoms, suspected iodine insufficiency, or those who have had borderline spot urine results and want a clearer answer.
The test involves a 24-hour urine collection, which requires planning but is straightforward to complete at home. You can continue normal activities during the collection period. Your practitioner will interpret the result in the context of your thyroid function, symptoms, and dietary history before making any recommendations about iodine support.
Suited to people with thyroid concerns, suspected iodine deficiency or those who want a thorough assessment of whole-body iodine stores beyond what a spot test provides.
