Detecting iodine deficiency

School age children

Median urinary iodine concentration (microgram/L)	Indication of population iodine intake	Indication of population iodine status
< 20	Insufficient	Severe iodine deficiency
20-49	Insufficient	Moderate iodine deficiency
50-99	Insufficient	Mild iodine deficiency
100-199	Adequate	Adequate iodine nutrition
200-299	Above requirements	May pose a slight risk of more than adequate iodine intake in these populations
≥ 300	Excessive	Risk of adverse health consequences (iodine-induced hyperthyroidism, autoimmune thyroid disease)

Pregnant women

Median urinary iodine concentration (microgram/L)	Indication of population iodine intake	Indication of population iodine status
<150	Insufficient
150-249	Adequate
250-499	Above requirements
≥500	Excessive

Lactating women and children under 2 years of age

Median urinary iodine concentration (microgram/L)	Indication of population iodine intake	Indication of population iodine status
≥500	Insufficient
≥100	Adequate

It is important to note that only population-level assessments of iodine status are possible from the survey methodology of casual, spot urine sample collection. Iodine status estimates based on the methodology of casual spot urine sample collection cannot be used to classify individual status and should not be presented as a prevalence of deficiency or adequacy. The information provided in the table above is frequently misinterpreted to reflect the situation of individuals. The correct interpretation is that populations with a median urinary iodine <20 microgram/L have “severe” iodine deficiency, populations with a median urinary iodine 20-49 microgram/L have “moderate” iodine deficiency, and populations with a median urinary iodine 50-99 microgram/L have “mild” iodine deficiency.

References

Urinary iodine concentrations for determining iodine status deficiency in populations. Vitamin and Mineral Nutrition Information System. Geneva: World Health Organization; 2013.