What does the Urinary Iodine test measure?

Why is Urinary Iodine measured?

Urinary iodine assesses adequacy rather than toxicity. Low values (<100 µg/L) suggest iodine insufficiency, a cause of goitre and hypothyroidism. High values (>300 µg/L) can reflect excessive supplementation or exposure and, in susceptible individuals, precipitate thyroid dysfunction.

Reference ranges

Standard reference

WHO defines population adequacy as median 100–199 µg/L; individual spot results interpreted with caution.

Functional medicine optimal

Population median 100–199 µg/L; individual interpretation requires context and, ideally, multiple samples.

Units

µg/g creatinine, µg/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.