Urinary iodine percentile ranges in the United States

The status of iodine nutrition of a population can be determined by measurement of urinary iodine concentrations since it is thought to indicate dietary iodine intake. Normally, these results are compared to population-based criteria, since there are no reference ranges for urinary iodine.

To determine the percentile ranges for urinary iodide (UI) concentrations in normal individuals in the United States.

The third National Health and Nutrition Examination Survey (NHANES III) (1988-1994) database of the civilian, non-institutionalized, iodine-sufficient US population was used. The 2.5th to 97.5th percentile ranges for urinary iodine and for urinary iodine per gram creatinine ratio (UI/Cr) (microg/g) were calculated for females and males, 6-89 years of age, each stratified by age groups.

We calculated the percentile ranges for urinary iodine. After exclusions of subjects with goiter or thyroid disease, the study sample included 21,530 subjects; 10,439 males and 11,091 females. For women of childbearing age (14-44 years), urinary iodine concentration 2.5th to 97.5th percentiles are 1.8-65 microg/dl or 36-539 microg/g creatinine. For pregnant women, the ranges are 4.2-55 microg/dl or 33-535 microg/g creatinine.