Providing comprehensive assessment of iodine sufficiency and antagonistic halides in a single test, the Urine Halides test assesses iodine as well as exposure to and retention of bromide and fluoride. Iodine is an essential element required for normal function of the thyroid gland and immune system, and the integrity of breast tissue. Bromide and fluoride are non-essential, antagonistic halides that can disrupt iodine homeostasis and function. The test can be performed using conventional random or 24-hour urine collection or after administration of a loading dose of iodide/iodine. Iodine and bromine are measured by ICP-MS, as is used by the CDC.